handle null vertex or index buffers in batch

src/gpu/GrAAConvexPathRenderer.cpp

Index: src/gpu/GrAAConvexPathRenderer.cpp
diff --git a/src/gpu/GrAAConvexPathRenderer.cpp b/src/gpu/GrAAConvexPathRenderer.cpp
index 3ab8af5c374b21f53d65a3cd36eeb24bb5594254..317f9a0f8d037c93755b631ff9a0c15b4fa02ef1 100644
--- a/src/gpu/GrAAConvexPathRenderer.cpp
+++ b/src/gpu/GrAAConvexPathRenderer.cpp
@@ -784,6 +784,11 @@ public:
                                                                   &vertexBuffer,
                                                                   &firstVertex);
 
+            if (!vertices) {
+                SkDebugf("Could not allocate vertices\n");
+                return;
+            }
+
             const GrIndexBuffer* indexBuffer;
             int firstIndex;
 
@@ -791,6 +796,11 @@ public:
                                                                 &indexBuffer,
                                                                 &firstIndex);
 
+            if (!indices) {
+                SkDebugf("Could not allocate indices\n");
+                return;
+            }
+
             QuadVertex* verts = reinterpret_cast<QuadVertex*>(vertices);
             uint16_t* idxs = reinterpret_cast<uint16_t*>(indices);