add fail condition to addexpanded

src/pathops/SkOpCoincidence.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkOpCoincidence.h"
 #include "SkOpSegment.h"
 #include "SkPathOpsTSect.h"
 
@@ skipping 118 matching lines @@
                 }
                 // start over
                 test = start;
                 oTest = oStart;
             }
             if (test != end) {
                 test = test->upCast()->next();
             }
             if (oTest != oEnd) {
                 oTest = coin->fFlipped ? oTest->prev() : oTest->upCast()->next();
+                if (!oTest) {
+                    return false;
+                }
             }
         }
     } while ((coin = coin->fNext));
 #if DEBUG_VALIDATE
     globalState->setPhase(SkOpGlobalState::kWalking);
 #endif
     return true;
 }
 
 bool SkOpCoincidence::addIfMissing(const SkCoincidentSpans* outer, SkOpPtT* over1s,
@@ skipping 537 matching lines @@
     *overS = SkTMax(SkTMin(coin1s->fT, coin1e->fT), SkTMin(coin2s->fT, coin2e->fT));
     *overE = SkTMin(SkTMax(coin1s->fT, coin1e->fT), SkTMax(coin2s->fT, coin2e->fT));
     return *overS < *overE;
 }
 
 bool SkOpCoincidence::testForCoincidence(const SkCoincidentSpans* outer, const SkOpPtT* testS,
         const SkOpPtT* testE) const {
     return testS->segment()->testForCoincidence(testS, testE, testS->span(),
             testE->span(), outer->fCoinPtTStart->segment(), 120000);  // FIXME: replace with tuned
 }