compiler: Don't make erroneous type descriptors.
compiler: Don't make erroneous type descriptors.

There is no need to make type descriptors for named types when there
are errors during package compilation.  Particularly, if the error in
package compilation is from a malformed named type, there is no
guarantee a type descriptor can be created.

Fixes golang/go#11560.

Change-Id: Ieb46b05cd91f4a9d2fd83883cba5011f7a65aab8
Reviewed-on: https://go-review.googlesource.com/12792
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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