Fix a memory leak

If nLayers is insane, we won't properly free `video` in the `fail`
block, since the nLayers check is done before we assign `video` to
`decCtrl->videoDecoderData`.

Caught by the static analyzer.

Bug: None
Test: Ran the analyzer again. It no longer complains about this leak.

Change-Id: I6ec612b75f9d325c7693f670a96d95363f6bb2ae