fix fuzz

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 974 matching lines @@
             largest = test;
             lCollapsed = test->fCollapsed;
         }
     }
     return largest;
 }
 
 template<typename TCurve, typename OppCurve>
 bool SkTSect<TCurve, OppCurve>::coincidentCheck(SkTSect<OppCurve, TCurve>* sect2) {
     SkTSpan<TCurve, OppCurve>* first = fHead;
+    if (!first) {
+        return false;
+    }
     SkTSpan<TCurve, OppCurve>* last, * next;
     do {
         int consecutive = this->countConsecutiveSpans(first, &last);
         next = last->fNext;
         if (consecutive < COINCIDENT_SPAN_COUNT) {
             continue;
         }
         this->validate();
         sect2->validate();
         this->computePerpendiculars(sect2, first, last);
@@ skipping 1391 matching lines @@
             --last;
         } else {
             intersections->setCoincident(index++);
         }
         intersections->setCoincident(index);
     }
     SkOPOBJASSERT(intersections, intersections->used() <= TCurve::kMaxIntersections);
 }
 
 #endif