fix one more fuzzer

src/pathops/SkOpCoincidence.cpp

Index: src/pathops/SkOpCoincidence.cpp
diff --git a/src/pathops/SkOpCoincidence.cpp b/src/pathops/SkOpCoincidence.cpp
index ef0ea60cc8ccb24e02da535a68b71e1fee65fbb8..1390533a51a025cc92cffd6e673f9883f9a168f5 100755
--- a/src/pathops/SkOpCoincidence.cpp
+++ b/src/pathops/SkOpCoincidence.cpp
@@ -864,6 +864,7 @@ bool SkOpCoincidence::addOverlap(const SkOpSegment* seg1, const SkOpSegment* seg
     }
     const SkOpPtT* s2 = overS->find(seg2);
     const SkOpPtT* e2 = overE->find(seg2);
+    FAIL_IF(!s2);
     FAIL_IF(!e2);
     if (!s2->starter(e2)->span()->upCast()->windValue()) {
         s2 = overS->find(seg2o);