If a data provider enters the suspended state, then is requested to
exit its thread, it could exit handle_suspension() without creating a
decoder. After this, we weren't checking if we should continue handling
seeks/data decoding. Thus, we got to push_data_and_decode_some_frames()
without a decoder and crashed.
Instead, always skip an iteration of the thread loop when the suspend
finishes, so that the loop has a change to exit.
786bc63aaa