demux: avi: fix master track selection with nonseekable

(otherwise drops packets)

modules/demux/avi/avi.c

@@ -1331,15 +1331,19 @@ static int Demux_UnSeekable( demux_t *p_demux )
             b |= b_extra;
         }
 
-        if( b && tk->i_cat == VIDEO_ES )
+        if( b )
+        {
+            if( tk->i_cat == VIDEO_ES )
             {
                 p_stream_master = tk;
+                break;
             }
-        else if( b )
+            else if( !tk )
             {
                 p_stream_master = tk;
             }
         }
+    }
 
     if( !p_stream_master )
     {