[M52] add fail condition to addexpanded

src/pathops/SkOpCoincidence.cpp

Index: src/pathops/SkOpCoincidence.cpp
diff --git a/src/pathops/SkOpCoincidence.cpp b/src/pathops/SkOpCoincidence.cpp
index 130d1daff777eb392cf6183223b3035eeecc1ea3..9ef4e0ac3826f47f533ee1dd3030c326ca3680de 100755
--- a/src/pathops/SkOpCoincidence.cpp
+++ b/src/pathops/SkOpCoincidence.cpp
@@ -133,6 +133,9 @@ bool SkOpCoincidence::addExpanded(SkChunkAlloc* allocator
             }
             if (oTest != oEnd) {
                 oTest = coin->fFlipped ? oTest->prev() : oTest->upCast()->next();
+                if (!oTest) {
+                    return false;
+                }
             }
         }
     } while ((coin = coin->fNext));