Fix T54076: MCE in Graph mode - clip.graph_select_border does not work by header menu

While the script should be using INVOKE_PREVIEW for operators in clip view,
window manager was lacking some switch statements.

Thanks Brecht fore review!

source/blender/windowmanager/intern/wm_event_system.c

@@ -1279,6 +1279,8 @@ static int wm_operator_call_internal(
 		switch (context) {
 			case WM_OP_INVOKE_DEFAULT:
 			case WM_OP_INVOKE_REGION_WIN:
+			case WM_OP_INVOKE_REGION_PREVIEW:
+			case WM_OP_INVOKE_REGION_CHANNELS:
 			case WM_OP_INVOKE_AREA:
 			case WM_OP_INVOKE_SCREEN:
 				/* window is needed for invoke, cancel operator */