crash when run rule example in gherkin reference

### 👓 What did you see?

run below feature crah
https://cucumber.io/docs/gherkin/reference/#keywords
`Feature: Highlander

Rule: There can be only One

Example: Only One -- More than one alive
Given there are 3 ninjas
And there are more than one ninja alive
When 2 ninjas meet, they will fight
Then one ninja dies (but not me)
And there is one ninja less alive

Example: Only One -- One alive
Given there is only 1 ninja alive
Then he (or she) will live forever ;-)`

`Feature: Highlander
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=0x70 pc=0x1195855]

goroutine 1 [running]:
github.com/cucumber/godog/internal/formatters.(*Pretty).printStep(0xc000012b80, 0xc0002e8090, 0xc0002b8680)
/Users/long/go/pkg/mod/github.com/cucumber/godog@v0.12.5/internal/formatters/fmt_pretty.go:384 +0x6d5`
### ✅ What did you expect to see?
no crash

no crash
### 📦 Which tool/library version are you using?

0.12.5
### 🔬 How could we reproduce it?

Steps to reproduce the behavior:
1. Install '...' version '...'
2. Create a file called '....'
3. Run command '....'
4. See error '....'

### 📚 Any additional context?

----

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Start by running the Rule and Example from the Gherkin reference with godog 0.12.5 and reproduce the reported panic. Inspect the stack-trace location in internal/formatters/fmt_pretty.go:384; done means the example runs without a nil-pointer crash.

Written by the indexing model from the issue text.