SIGSEGV when root identifier for a workflow does not match an object in the schema

[dustinblack]

Describe the bug

If the root reference in a workflow schema does not match an object ID, a SIGSEGV panic is emitted.

$ arcaflow -config config.yaml -input input.yaml -context .
2024-03-01T13:03:55+01:00	debug	source=deployer	Checking whether image exists with command [/usr/bin/podman image ls --format {{.Repository}}:{{.Tag}}]
2024-03-01T13:03:57+01:00	debug	source=deployer	quay.io/arcalot/arcaflow-plugin-example:0.5.0: image already present skipping pull
2024-03-01T13:03:57+01:00	debug	source=deployer	Deploying with command [/usr/bin/podman run -i -a stdin -a stdout -a stderr --name arcaflow_podman_QNODKTZxeD quay.io/arcalot/arcaflow-plugin-example:0.5.0 --atp]
2024-03-01T13:03:57+01:00	debug	source=plugin-provider	Reading plugin schema...
2024-03-01T13:03:57+01:00	debug	source=plugin-provider	Hello message read, ATP version 3.
2024-03-01T13:03:57+01:00	debug	source=plugin-provider	Schema unserialization complete.
2024-03-01T13:03:57+01:00	debug	source=deployer	Killing with command [/usr/bin/podman kill arcaflow_podman_QNODKTZxeD]
2024-03-01T13:03:57+01:00	warning	source=deployer	failed to kill pod arcaflow_podman_QNODKTZxeD, probably the execution terminated earlier
2024-03-01T13:03:57+01:00	debug	source=deployer	Removing container with command [/usr/bin/podman rm --force arcaflow_podman_QNODKTZxeD]
2024-03-01T13:03:57+01:00	info	source=deployer	successfully removed container arcaflow_podman_QNODKTZxeD
2024-03-01T13:03:57+01:00	info	source=deployer	stdin pipe successfully closed
2024-03-01T13:03:57+01:00	info	source=deployer	stdout pipe successfully closed
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x152d08]

goroutine 1 [running]:
go.flow.arcalot.io/pluginsdk/schema.(*ScopeSchema).Properties(0xfffea6ae6358?)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/pluginsdk@v0.5.1/schema/scope.go:63 +0x38
go.flow.arcalot.io/expressions.dependenciesBracketKey({0x1630bb0, 0x400046aae0}, {0x10b6400?, 0x4000014150}, 0x40004cd410)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/expressions@v0.2.1/expression_dependencies.go:231 +0x6c0
go.flow.arcalot.io/expressions.(*dependencyContext).identifierDependencies(0x400083ed28?, 0x400016c6a0?, {0x1630bb0, 0x400046aae0}, 0xfffea6f23800?)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/expressions@v0.2.1/expression_dependencies.go:170 +0x8c
go.flow.arcalot.io/expressions.(*dependencyContext).dependencies(0x40004cd3e0?, {0x1623120?, 0x40001534e0?}, {0x1630bb0?, 0x400046aae0?}, 0xfffea6dae068?)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/expressions@v0.2.1/expression_dependencies.go:41 +0xf8
go.flow.arcalot.io/expressions.(*dependencyContext).dotNotationDependencies(0x0?, 0x400016c6c0, {0x1630bb0?, 0x400063f170?}, 0x28?)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/expressions@v0.2.1/expression_dependencies.go:62 +0x90
go.flow.arcalot.io/expressions.(*dependencyContext).dependencies(0x4000648000?, {0x16230f0?, 0x400016c6c0?}, {0x1630bb0?, 0x400063f170?}, 0x1375f9d?)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/expressions@v0.2.1/expression_dependencies.go:34 +0x78
go.flow.arcalot.io/expressions.expression.Dependencies({{0x40009003e0?, 0x15?}, {0x16230f0?, 0x400016c6c0?}}, {0x1630bb0, 0x400063f170}, 0x40008d2a80)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/expressions@v0.2.1/expression.go:78 +0xa4
go.flow.arcalot.io/engine/workflow.(*executor).prepareDependencies(0x112cdc0?, 0x40000140d0?, {0x11cc4e0, 0x400016c760}, {0x1631300, 0x40004ccbd0}, 0x400083f0c8?, {0x16306b0, 0x400016dac0})
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/workflow/executor.go:795 +0x3cc
go.flow.arcalot.io/engine/workflow.(*executor).prepareDependencies(0x112cdc0?, 0x4000014010?, {0x11511c0, 0x4000904db0}, {0x1631300, 0x40004ccbd0}, 0x400083f2c8?, {0x16306b0, 0x400016dac0})
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/workflow/executor.go:859 +0xb90
go.flow.arcalot.io/engine/workflow.(*executor).prepareDependencies(0x11511c0?, 0x40004cd380?, {0x11511c0, 0x4000904d80}, {0x1631300, 0x40004ccbd0}, 0x11531a0?, {0x16306b0, 0x400016dac0})
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/workflow/executor.go:859 +0xb90
go.flow.arcalot.io/engine/workflow.(*executor).connectStepDependencies(0x4000904ed0?, 0x16347d0?, 0x400046aae0?, 0x400016dac0?, {0x16306b0, 0x400016dac0?}, 0x1154c40?)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/workflow/executor.go:320 +0x57c
go.flow.arcalot.io/engine/workflow.(*executor).Prepare(0x4000904ed0, 0x40005460a0, 0x40008d2a80)
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/workflow/executor.go:120 +0x218
go.flow.arcalot.io/engine.workflowEngine.Parse({{0x162fbc0, 0x40008d2ab0}, {0x162e8f8, 0x40005938f0}, 0x4000490180}, 0x4eedc?, {0x400048e320?, 0xfceed4?})
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/engine.go:107 +0x170
main.runWorkflow({0x161e290, 0x40008d32f0}, 0x13786d5?, {0x400048e320, 0x48}, {0x162fbc0?, 0x40008d2a20}, {0x4000296800, 0x11, 0x200})
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/cmd/arcaflow/main.go:204 +0x1a8
main.main()
	/home/runner/go/pkg/mod/go.flow.arcalot.io/engine@v0.9.1/cmd/arcaflow/main.go:190 +0xd04

To reproduce

Simply reproduced with any workflow:

version: v0.2.0
input:
  root: BadObjectName
  objects:
    RootObject:
      id: RootObject
      properties:
        nickname:
          display:
            description: Just a name
            name: Name
          required: true
          type:
            type_id: string

steps: 
  example:
    plugin:
      deployment_type: image
      src: quay.io/arcalot/arcaflow-plugin-example:0.5.0
    input:
      name:
        _type: nickname
        nick: !expr $.input.nickname

outputs:
 success:
   example: !expr $.steps.example.outputs.success