fix cubic linear test

src/pathops/SkOpBuilder.cpp

Index: src/pathops/SkOpBuilder.cpp
diff --git a/src/pathops/SkOpBuilder.cpp b/src/pathops/SkOpBuilder.cpp
index d0cb9c1de914ac8ae4c1e6ffb680fbf3d0331269..e4e7834392d14bf0f58323d4e5ca3d5389f17daf 100644
--- a/src/pathops/SkOpBuilder.cpp
+++ b/src/pathops/SkOpBuilder.cpp
@@ -53,7 +53,9 @@ bool FixWinding(SkPath* path) {
     if (!contourHead.count()) {
         return true;
     }
-    SkASSERT(contourHead.next());
+    if (!contourHead.next()) {
+        return false;
+    }
     contourHead.joinAllSegments();
     contourHead.resetReverse();
     bool writePath = false;