decoder: don't flush if already flushed
decoder: don't flush if already flushed

This commit fixes the following assert in the DecoderThread function:
"assert( vlc_fifo_IsEmpty( p_owner->p_fifo) );"

Indeed, if input_DecoderFlush is called again (just after), p_owner->flushed
will be true and the input won't wait for the DecoderThread. As a consequence,
the input will send blocks while the DecoderThread is flushing, hence the
assert.

Signed-off-by: Rémi Denis-Courmont <f0699137713be92736351a0674e79536595e4a60@remlab.net>

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc