Ignore switch-case with non-String values for mimeType check

Errorprone ensures mimeType checks to be case insensitive. Updated the
check to ignore switch-case with non-String values.

Bug: 204167423
Test: m -j32 RUN_ERROR_PRONE=true

Change-Id: Ia879b262887ec87b7e3418ff76d5b69bf848a552
1 file changed