fix fuzzes

src/pathops/SkPathOpsTSect.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkPathOpsTSect_DEFINED
 #define SkPathOpsTSect_DEFINED
 
 #include "SkChunkAlloc.h"
@@ skipping 1202 matching lines @@
         SkTSwap(oppStartT, oppEndT);
     }
     SkOPASSERT(oppStartT < oppEndT);
     SkASSERT(coinStart == first->fStartT);
     SkASSERT(coinEnd == last->fEndT);
     SkOPASSERT(oppStartT == oppFirst->fStartT);
     SkOPASSERT(oppEndT == oppLast->fEndT);
     if (!oppFirst) {
         return nullptr;
     }
+    if (!oppLast) {
+        return nullptr;
+    }
     // reduce coincident runs to single entries
     this->validate();
     sect2->validate();
     bool deleteEmptySpans = this->updateBounded(first, last, oppFirst);
     deleteEmptySpans |= sect2->updateBounded(oppFirst, oppLast, first);
     this->removeSpanRange(first, last);
     sect2->removeSpanRange(oppFirst, oppLast);
     first->fEndT = last->fEndT;
     first->resetBounds(this->fCurve);
     first->fCoinStart.setPerp(fCurve, first->fStartT, first->fPart[0], sect2->fCurve);
@@ skipping 1062 matching lines @@
             --last;
         } else {
             intersections->setCoincident(index++);
         }
         intersections->setCoincident(index);
     }
     SkASSERT(intersections->used() <= TCurve::kMaxIntersections);
 }
 
 #endif