- listener for sequencer space panels added for frame changes, now redraws during transform

- invalid pointer was used for getting the sequencer length crashing blender or setting the length to negative values.
- printf_strip(seq) for debugging sequence strip locations
- Spelling: Cheet Sheet -> Cheat Sheet

source/blender/editors/space_sequencer/space_sequencer.c

@@ -245,6 +245,14 @@ static void sequencer_buttons_area_listener(ARegion *ar, wmNotifier *wmn)
 {
 	/* context changes */
 	switch(wmn->category) {
+		case NC_SCENE:
+		switch(wmn->data) {
+			case ND_FRAME:
+			case ND_SEQUENCER:
+				ED_region_tag_redraw(ar);
+				break;
+		}
+		break;
 		case NC_SPACE:
 			if(wmn->data == ND_SPACE_SEQUENCER)
 				ED_region_tag_redraw(ar);