Preview of nil content bad response

[lisandromaselli]

Version:

• listmonk: v2.3.0
• OS: docker

Description of the bug and steps to reproduce:
Preview of a nil content returns 502.

Description:
echo: http: panic serving ...: runtime error: invalid memory address or nil pointer dereference
goroutine 167 [running]:
net/http.(*conn).serve.func1()
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:1802 +0xb9
panic({0xb07d60, 0x11c0780})
/opt/hostedtoolcache/go/1.17.13/x64/src/runtime/panic.go:1047 +0x266
html/template.(*Template).lookupAndEscapeTemplate(0x0, {0xbadd96, 0x4})
/opt/hostedtoolcache/go/1.17.13/x64/src/html/template/template.go:146 +0x50
html/template.(*Template).ExecuteTemplate(0xc0003dab60, {0xcdcae0, 0xc0003d6810}, {0xbadd96, 0xc00080cfd0}, {0xb2a2a0, 0xc0000ff200})
/opt/hostedtoolcache/go/1.17.13/x64/src/html/template/template.go:135 +0x38
github.com/knadh/listmonk/internal/manager.(*CampaignMessage).render(0xc0000ff200)
/home/runner/work/listmonk/listmonk/internal/manager/manager.go:752 +0x13f
github.com/knadh/listmonk/internal/manager.(*Manager).NewCampaignMessage(_, , {{0x0, {{0x0, 0x0, 0x0}, 0x0}, {{0x0, 0x0, 0x0}, ...}}, ...})
/home/runner/work/listmonk/listmonk/internal/manager/manager.go:198 +0x215
main.handlePreviewCampaign({0xd073d0, 0xc0015879a0})
/home/runner/work/listmonk/listmonk/cmd/campaigns.go:144 +0x6e5
github.com/labstack/echo/v4/middleware.BasicAuthWithConfig.func1.1({0xd073d0, 0xc0015879a0})
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/middleware/basic_auth.go:93 +0x4a5
github.com/labstack/echo/v4.(*Echo).add.func1({0xd073d0, 0xc0015879a0})
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/echo.go:536 +0x51
main.initHTTPServer.func1.1({0xd073d0, 0xc0015879a0})
/home/runner/work/listmonk/listmonk/cmd/init.go:684 +0x5f
github.com/labstack/echo/v4.(*Echo).ServeHTTP(0xc0001c4000, {0xce9cd8, 0xc000532000}, 0xc00020a200)
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/echo.go:646 +0x3bc
net/http.serverHandler.ServeHTTP({0xc0003d64e0}, {0xce9cd8, 0xc000532000}, 0xc00020a200)
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:2879 +0x43b
net/http.(*conn).serve(0xc000d4c5a0, {0xced9a0, 0xc0005f89f0})
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:1930 +0xb08
created by net/http.(*Server).Serve
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:3034 +0x4e8
echo: http: panic serving 168.119.166.131:45000: runtime error: invalid memory address or nil pointer dereference
goroutine 202 [running]:
net/http.(*conn).serve.func1()
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:1802 +0xb9
panic({0xb07d60, 0x11c0780})
/opt/hostedtoolcache/go/1.17.13/x64/src/runtime/panic.go:1047 +0x266
html/template.(*Template).lookupAndEscapeTemplate(0x0, {0xbadd96, 0x4})
/opt/hostedtoolcache/go/1.17.13/x64/src/html/template/template.go:146 +0x50
html/template.(*Template).ExecuteTemplate(0xc00029cc30, {0xcdcae0, 0xc000d5c390}, {0xbadd96, 0xc0003bcfd0}, {0xb2a2a0, 0xc00055ab40})
/opt/hostedtoolcache/go/1.17.13/x64/src/html/template/template.go:135 +0x38
github.com/knadh/listmonk/internal/manager.(*CampaignMessage).render(0xc00055ab40)
/home/runner/work/listmonk/listmonk/internal/manager/manager.go:752 +0x13f
github.com/knadh/listmonk/internal/manager.(*Manager).NewCampaignMessage(, , {{0x0, {{0x0, 0x0, 0x0}, 0x0}, {{0x0, 0x0, 0x0}, ...}}, ...})
/home/runner/work/listmonk/listmonk/internal/manager/manager.go:198 +0x215
main.handlePreviewCampaign({0xd073d0, 0xc0015872c0})
/home/runner/work/listmonk/listmonk/cmd/campaigns.go:144 +0x6e5
github.com/labstack/echo/v4/middleware.BasicAuthWithConfig.func1.1({0xd073d0, 0xc0015872c0})
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/middleware/basic_auth.go:93 +0x4a5
github.com/labstack/echo/v4.(*Echo).add.func1({0xd073d0, 0xc0015872c0})
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/echo.go:536 +0x51
main.initHTTPServer.func1.1({0xd073d0, 0xc0015872c0})
/home/runner/work/listmonk/listmonk/cmd/init.go:684 +0x5f
github.com/labstack/echo/v4.(*Echo).ServeHTTP(0xc0001c4000, {0xce9cd8, 0xc0000e8000}, 0xc000164100)
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/echo.go:646 +0x3bc
net/http.serverHandler.ServeHTTP({0xc000d5c0c0}, {0xce9cd8, 0xc0000e8000}, 0xc000164100)
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:2879 +0x43b
net/http.(*conn).serve(0xc001587220, {0xced9a0, 0xc0005f89f0})
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:1930 +0xb08
created by net/http.(*Server).Serve
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:3034 +0x4e8
echo: http: panic serving ....: runtime error: invalid memory address or nil pointer dereference
goroutine 214 [running]:
net/http.(*conn).serve.func1()
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:1802 +0xb9
panic({0xb07d60, 0x11c0780})
/opt/hostedtoolcache/go/1.17.13/x64/src/runtime/panic.go:1047 +0x266
html/template.(*Template).lookupAndEscapeTemplate(0x0, {0xbadd96, 0x4})
/opt/hostedtoolcache/go/1.17.13/x64/src/html/template/template.go:146 +0x50
html/template.(*Template).ExecuteTemplate(0xc00029cc30, {0xcdcae0, 0xc000d5c420}, {0xbadd96, 0xc00008efd0}, {0xb2a2a0, 0xc00055b560})
/opt/hostedtoolcache/go/1.17.13/x64/src/html/template/template.go:135 +0x38
github.com/knadh/listmonk/internal/manager.(*CampaignMessage).render(0xc00055b560)
/home/runner/work/listmonk/listmonk/internal/manager/manager.go:752 +0x13f
github.com/knadh/listmonk/internal/manager.(*Manager).NewCampaignMessage(, _, {{0x0, {{0x0, 0x0, 0x0}, 0x0}, {{0x0, 0x0, 0x0}, ...}}, ...})
/home/runner/work/listmonk/listmonk/internal/manager/manager.go:198 +0x215
main.handlePreviewCampaign({0xd073d0, 0xc0004a4d20})
/home/runner/work/listmonk/listmonk/cmd/campaigns.go:144 +0x6e5
github.com/labstack/echo/v4/middleware.BasicAuthWithConfig.func1.1({0xd073d0, 0xc0004a4d20})
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/middleware/basic_auth.go:93 +0x4a5
github.com/labstack/echo/v4.(*Echo).add.func1({0xd073d0, 0xc0004a4d20})
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/echo.go:536 +0x51
main.initHTTPServer.func1.1({0xd073d0, 0xc0004a4d20})
/home/runner/work/listmonk/listmonk/cmd/init.go:684 +0x5f
github.com/labstack/echo/v4.(*Echo).ServeHTTP(0xc0001c4000, {0xce9cd8, 0xc000d34000}, 0xc0015e2400)
/home/runner/go/pkg/mod/github.com/labstack/echo/v4@v4.9.0/echo.go:646 +0x3bc
net/http.serverHandler.ServeHTTP({0xc00054e330}, {0xce9cd8, 0xc000d34000}, 0xc0015e2400)
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:2879 +0x43b
net/http.(*conn).serve(0xc0004a4be0, {0xced9a0, 0xc0005f89f0})
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:1930 +0xb08
created by net/http.(*Server).Serve
/opt/hostedtoolcache/go/1.17.13/x64/src/net/http/server.go:3034 +0x4e8

[knadh]

A bug that results in a stack trace! Thanks for reporting this.