panic in pretty printing, when background step is longer than scenario step

[nightlyone]

given

Feature:
Background:
Given very long string here we cannot imagine how long

Scenario:
Given short

leads to panic in pretty printer.

The following patch fixes it for me:

--- a/fmt_pretty.go
+++ b/fmt_pretty.go
@@ -256,6 +256,9 @@ func (f *pretty) printStepKind(res *stepResult) {
        // first step of scenario, print header and calculate comment position
        case f.scenario != nil && f.steps == len(f.scenario.Steps):
                f.commentPos = f.longestStep(f.scenario.Steps, f.length(f.scenario))
+               if bgLength := f.longestStep(f.feature.Background.Steps, f.length(f.feature.Background)); bgLength > f.commentPos {
+                       f.commentPos = bgLength
+               }
                text := s(f.indent) + bcl(f.scenario.Keyword+": ", white) + f.scenario.Name
                text += s(f.commentPos-f.length(f.scenario)+1) + f.line(f.scenario.Location)
                fmt.Println("\n" + text)