Allow QueryParseException to escape ChangeQueryRewriter

ChangeIndex.getSource throws QueryParseException with the intention of
allowing implementations to not support certain operators/features
(e.g. regex queries). For this to result in a user-visible error
message instead of a 500, we need to not wrap it in an
IllegalStateException.

Change-Id: I8871df8b806cb48ba976ce00f5864a906cd3e9b3

gerrit-server/src/test/java/com/google/gerrit/server/index/IndexRewriteTest.java

@@ -327,7 +327,8 @@ public class IndexRewriteTest extends TestCase {
     return queryBuilder.parse(query);
   }
 
-  private Predicate<ChangeData> rewrite(Predicate<ChangeData> in) {
+  private Predicate<ChangeData> rewrite(Predicate<ChangeData> in)
+      throws QueryParseException {
     return rewrite.rewrite(in);
   }