Don't attempt to read chunks with bad length Fix #460

Former-commit-id: 86da0c1812ebb3db389d271edf6e8ca81167ba60
Former-commit-id: 93b28d11ed01296011abb4eb6bcb03c89e61ad49
Former-commit-id: 0ecfd461c9a6b5b2fe9aa8632534f8cbd5e0166c

src/ImageProcessorCore/Formats/Png/PngDecoderCore.cs

@@ -413,6 +413,11 @@ namespace ImageProcessorCore.Formats
                 return null;
             }
 
+            if (chunk.Length <= 0)
+            {
+                return null;
+            }
+
             byte[] typeBuffer = this.ReadChunkType(chunk);
 
             this.ReadChunkData(chunk);