allow conic chop to fail

gm/beziereffects.cpp

Index: gm/beziereffects.cpp
diff --git a/gm/beziereffects.cpp b/gm/beziereffects.cpp
index 42be080ae3b707a3a61b1be28ed0c8b7ce68f8a4..3dd4d65f7f7c9026b06390f31536b19b167cf0ba 100644
--- a/gm/beziereffects.cpp
+++ b/gm/beziereffects.cpp
@@ -353,7 +353,10 @@ private:
             if (dst) {
                 SkConic conic;
                 conic.set(src, weight);
-                conic.chopAt(t, dst);
+                if (!conic.chopAt(t, dst)) {
+                    dst[0].set(src, weight);
+                    return 1;
+                }
             }
             return 2;
         }