Fix unknown-identifier issue discovered by fuzzer.

This error was caused by an unbalanced symbol table push. This could
occur when an interface block encountered an error while parsing its
var-decls.

Change-Id: I910a980ac92fac7c0786c48b8dc3003ee3e75e5b
Bug: oss-fuzz:26700
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/330896
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
4 files changed