compiler: Don't crash on erroneous array types.
compiler: Don't crash on erroneous array types.

Fixes golang/go#11546.

Change-Id: I275a97c3216385516ba5e3f87952ecd4d147ae8b
Reviewed-on: https://go-review.googlesource.com/13795
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

qskycolor/gofrontend,golang/gofrontend,golang/gofrontend,qskycolor/gofrontend,golang/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,qskycolor/gofrontend,golang/gofrontend,qskycolor/gofrontend