Region cannot handle malformed Rects. Abort the Region op in that case.

Bug: 5331198, 5334829
Change-Id: Ib1fdbf6fb291e7f1191ccfe16b5ff29d73e7a474
diff --git a/libs/ui/Region.cpp b/libs/ui/Region.cpp
index 8dab291..5656088 100644
--- a/libs/ui/Region.cpp
+++ b/libs/ui/Region.cpp
@@ -482,6 +482,7 @@
     if (!rhs.isValid()) {
         LOGE("Region::boolean_operation(op=%d) invalid Rect={%d,%d,%d,%d}",
                 op, rhs.left, rhs.top, rhs.right, rhs.bottom);
+        return;
     }
 
 #if VALIDATE_WITH_CORECG || VALIDATE_REGIONS