Propagate validation errors

src/core/SkPictureData.h

Index: src/core/SkPictureData.h
diff --git a/src/core/SkPictureData.h b/src/core/SkPictureData.h
index 0e351509bc91858cf59c3e4f7990bddf832440aa..353bbd935762ac484b44956a715ab5061f0243e6 100644
--- a/src/core/SkPictureData.h
+++ b/src/core/SkPictureData.h
@@ -117,6 +117,9 @@ public:
 
     const SkPaint* getPaint(SkReadBuffer* reader) const {
         const int index = reader->readInt() - 1;
+        if (index == -1) {  // recorder wrote a zero for no paint (likely drawimage)
+            return nullptr;
+        }
         return reader->validateIndex(index, fPaints.count()) ? &fPaints[index] : nullptr;
     }