fix for [#12218] Impossible to exit meta strips with hotkey

Only enter mesta's that are active and selected, inconsistent with editmode in the 3D view, but editmode dosnt deal with 
nested data.

source/blender/src/editseq.c

@@ -2890,7 +2890,7 @@ void enter_meta(void)
 	ed= G.scene->ed;
 	if(ed==0) return;
 
-	if(last_seq==0 || last_seq->type!=SEQ_META || last_seq->flag==0) {
+	if(last_seq==0 || last_seq->type!=SEQ_META || (last_seq->flag & SELECT)==0) {
 		exit_meta();
 		return;
 	}