fix fuzz

src/pathops/SkPathOpsCommon.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkAddIntersections.h"
 #include "SkOpCoincidence.h"
 #include "SkOpEdgeBuilder.h"
 #include "SkPathOpsCommon.h"
@@ skipping 106 matching lines @@
     #endif
             return last->segment();
         }
         if (done) {
             continue;
         }
         // find first angle, initialize winding to computed wind sum
         int winding;
         bool sortable;
         const SkOpAngle* angle = AngleWinding(*startPtr, *endPtr, &winding, &sortable);
+        if (!angle) {
+            return nullptr;
+        }
         if (winding == SK_MinS32) {
             continue;
         }
         int sumWinding SK_INIT_TO_AVOID_WARNING;
         if (sortable) {
             segment = angle->segment();
             sumWinding = segment->updateWindingReverse(angle);
         }
         SkOpSegment* first = nullptr;
         const SkOpAngle* firstAngle = angle;
@@ skipping 443 matching lines @@
     }
 #if DEBUG_COINCIDENCE_VERBOSE
     coincidence->debugShowCoincidence();
 #endif
 #if DEBUG_COINCIDENCE
     coincidence->debugValidate();
 #endif
     SkPathOpsDebug::ShowActiveSpans(contourList);
     return true;
 }