fix: panic if a step in a job is nil

[ChristopherHX]

We need to be careful
Closes #1144

on: push
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
    -
    - run: exit 0

go run . -W .\w.yml -P ubuntu-latest=ubuntu:latest --no-skip-checkout
Error: invalid Step 0: missing run or uses key
exit status 1

[github-actions]

MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ CREDENTIALS	secretlint	yes		no	1.0s
✅ EDITORCONFIG	editorconfig-checker	2		0	0.53s
✅ GIT	git_diff	yes		no	0.0s

See errors details in artifact MegaLinter reports on CI Job page
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

[codecov]

Codecov Report

Merging #1145 (fc892da) into master (4f8da0a) will increase coverage by 2.49%.
The diff coverage is 78.48%.

@@            Coverage Diff             @@
##           master    #1145      +/-   ##
==========================================
+ Coverage   57.50%   60.00%   +2.49%     
==========================================
  Files          32       39       +7     
  Lines        4594     5000     +406     
==========================================
+ Hits         2642     3000     +358     
- Misses       1729     1751      +22     
- Partials      223      249      +26     

Impacted Files	Coverage Δ
pkg/model/action.go	0.00% <ø> (ø)
pkg/model/github_context.go	79.51% <ø> (ø)
pkg/model/planner.go	50.73% <ø> (+0.32%)	⬆️
pkg/model/workflow.go	50.36% <0.00%> (-0.56%)	⬇️
pkg/container/docker_run.go	5.01% <1.96%> (-0.53%)	⬇️
pkg/common/git.go	49.31% <28.57%> (-0.52%)	⬇️
pkg/container/file_collector.go	44.85% <44.85%> (ø)
pkg/runner/runner.go	73.72% <73.68%> (-2.75%)	⬇️
pkg/exprparser/interpreter.go	75.29% <75.00%> (+1.89%)	⬆️
pkg/runner/logger.go	69.56% <75.47%> (+4.13%)	⬆️
... and 20 more

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[KnisterPeter]

I think the main problem is found in this function:

act/pkg/model/workflow.go

Lines 416 to 428 in a76c349

	func (s *Step) Type() StepType {
	if s.Run != "" {
	if s.Uses != "" {
	return StepTypeInvalid
	}
	return StepTypeRun
	} else if strings.HasPrefix(s.Uses, "docker://") {
	return StepTypeUsesDockerURL
	} else if strings.HasPrefix(s.Uses, "./") {
	return StepTypeUsesActionLocal
	}
	return StepTypeUsesActionRemote
	}

It assumes that any type which isn't matched otherwise is a remote action.

[KnisterPeter]

I've created #1157 to fix this

[KnisterPeter]

Thanks 👍