decoder: fix potential NULL dereference

(cherry picked from commit 7df464879acb66d7a0a19905e3d48b7e6b5fcf33)

Conflicts:
	src/input/decoder.c

src/input/decoder.c

@@ -2017,7 +2017,8 @@ static int aout_update_format( decoder_t *p_dec )
 
         p_owner->p_aout = p_aout;
         DecoderUpdateFormatLocked( p_dec );
-        if( unlikely(p_owner->b_paused) ) /* fake pause if needed */
+        if( unlikely(p_owner->b_paused) && p_aout != NULL )
+            /* fake pause if needed */
             aout_DecChangePause( p_aout, true, mdate() );
 
         vlc_mutex_unlock( &p_owner->lock );