fix compareTo in FieldIndex

Author: Brian Chen

firebase-firestore/src/main/java/com/google/firebase/firestore/local/LocalDocumentsView.java

@@ -337,7 +337,6 @@ public Map<Document, Integer> getDocumentsBatchIdsMatchingCollectionGroupQuery(
       Query collectionQuery = query.asCollectionQueryAtPath(parent.append(collectionId));
       Map<Document, Integer> documentToBatchIds =
           getDocumentsMatchingCollectionQueryWithBatchId(collectionQuery, offset);
-      ;
       results.putAll(documentToBatchIds);
     }
     return results;

firebase-firestore/src/main/java/com/google/firebase/firestore/model/FieldIndex.java

@@ -176,7 +176,7 @@ public int compareTo(IndexOffset other) {
       if (cmp != 0) return cmp;
       cmp = getDocumentKey().compareTo(other.getDocumentKey());
       if (cmp != 0) return cmp;
-      return getLargestBatchId() < other.getLargestBatchId() ? -1 : 1;
+      return Integer.signum(getLargestBatchId() - other.getLargestBatchId());
     }
   }