x/auth/types: ModuleAccount.Validate() should check that its .BaseAccount is non-nil lest experience a crash

[odeke-em]

Summary of Bug

I found this panic but fuzzing cosmos/gaia/app whereby
This code in

cosmos-sdk/x/auth/types/account.go

Line 221 in bbb452f

if ma.Address != sdk.AccAddress(crypto.AddressHash([]byte(ma.Name))).String() {

presumes that .Address is always set having come from a composed ModuleAccount.BaseAccount, but that's a blind assumption which leads to a panic just by this code

func TestModuleAccountValidateNilBaseAccount(t *testing.T) {
        ma := &types.ModuleAccount{Name: "foo"}
        _ = ma.Validate()
}

which results in this crash

$ go test -run=NilBaseAccount
--- FAIL: TestModuleAccountValidateNilBaseAccount (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x100f4352d]

goroutine 417 [running]:
testing.tRunner.func1.2({0x1016e75a0, 0x102d7e660})
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1545 +0x238
testing.tRunner.func1()
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1548 +0x397
panic({0x1016e75a0?, 0x102d7e660?})
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/runtime/panic.go:914 +0x21f
github.com/cosmos/cosmos-sdk/x/auth/types.ModuleAccount.Validate({0x0, {0x1019ae75b, 0x3}, {0x0, 0x0, 0x0}})
	/Users/emmanuelodeke/go/src/github.com/cosmos/cosmos-sdk/x/auth/types/account.go:221 +0xed
github.com/cosmos/cosmos-sdk/x/auth/types_test.TestModuleAccountValidateNilBaseAccount(0x0?)
	/Users/emmanuelodeke/go/src/github.com/cosmos/cosmos-sdk/x/auth/types/genesis_test.go:141 +0x4e
testing.tRunner(0xc000568000, 0x101b497b0)
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1595 +0xff
created by testing.(*T).Run in goroutine 1
	/Users/emmanuelodeke/go/src/go.googlesource.com/go/src/testing/testing.go:1648 +0x3ad
exit status 2
FAIL	github.com/cosmos/cosmos-sdk/x/auth/types	0.614s

Version

The latest at 7c54a1c615e6f699b54ebd3ea20d7cd00890acd5

Remedy

Please check that ma.BaseAccount is non-nil

@@ -224,10 +217,7 @@
 	if strings.TrimSpace(ma.Name) == "" {
 		return errors.New("module account name cannot be blank")
 	}
-        if ma.BaseAccount == nil {
-                return errors.New("uninitialized ModuleAccount: BBaseAccount is nil")
-        }
-        
+

/cc @elias-orijtech