demux: libmp4: fix fwd null dereference (cid #1260237)
demux: dash: fix leak (cid #1260239)
demux: dash: missing initilializer (cid #1260241)
demux: dash: missing initializer (cid #1260242, #1260245)
demux: dash: remove unused member (cid #1260243)
demux: dash: missing initializer (cid #1260244)