fix fuzzes

src/pathops/SkPathOpsTSect.h

Index: src/pathops/SkPathOpsTSect.h
diff --git a/src/pathops/SkPathOpsTSect.h b/src/pathops/SkPathOpsTSect.h
index 85d3b10d954d76efc6555150e819222bece1fa7e..bd26e5ace3b5b6af3448b31b076999641aea1e0e 100644
--- a/src/pathops/SkPathOpsTSect.h
+++ b/src/pathops/SkPathOpsTSect.h
@@ -1220,6 +1220,9 @@ SkTSpan<TCurve, OppCurve>* SkTSect<TCurve, OppCurve>::extractCoincident(
     if (!oppFirst) {
         return nullptr;
     }
+    if (!oppLast) {
+        return nullptr;
+    }
     // reduce coincident runs to single entries
     this->validate();
     sect2->validate();