Fix possible crash

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
Fix bug #123

Libav had no timeout set for any of its functions. Now timeout callback
is added and set to 10 seconds.

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>
Removed unneeded this->

Signed-off-by: Rafał Malinowski <rafal.malinowski@corp.bluecherry.net>