fix: panic while running DRYRUN with local actions

[ChristopherHX]

With this change act's dryrun no longer panics after my previous change #719. An error is better than a panic.

We need to consider how act can support dryrun for localactions.

Closes #1140

[github-actions]

MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ CREDENTIALS	secretlint	yes		no	0.9s
✅ EDITORCONFIG	editorconfig-checker	1		0	0.58s
✅ 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 #1141 (d3b83e1) into master (4f8da0a) will increase coverage by 2.49%.
The diff coverage is 78.57%.

@@            Coverage Diff             @@
##           master    #1141      +/-   ##
==========================================
+ Coverage   57.50%   60.00%   +2.49%     
==========================================
  Files          32       39       +7     
  Lines        4594     4993     +399     
==========================================
+ Hits         2642     2996     +354     
- Misses       1729     1749      +20     
- Partials      223      248      +25     

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	50.91% <ø> (ø)
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

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