Fix bug in error handling that causes segfault

See: https://code.google.com/p/chromium/issues/detail?id=362697

The code properly catches an invalid stream but seg faults instead of
returning an error due to a buffer not having been initialized. This
code fixes that.

Change-Id: I695595e742cb08807e1dfb2f00bc097b3eae3a9b

test/invalid_file_test.cc

@@ -64,7 +64,7 @@ class InvalidFileTest
   FILE *res_file_;
 };
 
-TEST_P(InvalidFileTest, DISABLED_ReturnCode) {
+TEST_P(InvalidFileTest, ReturnCode) {
   const std::string filename = GET_PARAM(1);
   libvpx_test::CompressedVideoSource *video = NULL;