correct sloppy NULL checks, in interface code:

- uiPupMenuBegin was checking for NULL title but would still crash if it were NULL.
- now tag the function as 'nonnull' and remove NULL checks. make sure NULL isnt passed to it.

source/blender/editors/include/UI_interface.h

@@ -327,7 +327,11 @@ typedef void (*uiMenuHandleFunc)(struct bContext *C, void *arg, int event);
 
 typedef struct uiPopupMenu uiPopupMenu;
 
-struct uiPopupMenu *uiPupMenuBegin(struct bContext *C, const char *title, int icon);
+struct uiPopupMenu *uiPupMenuBegin(struct bContext *C, const char *title, int icon)
+#ifdef __GNUC__
+__attribute__((nonnull))
+#endif
+;
 void uiPupMenuEnd(struct bContext *C, struct uiPopupMenu *head);
 struct uiLayout *uiPupMenuLayout(uiPopupMenu *head);
 

source/blender/editors/interface/interface_handlers.c

@@ -4944,7 +4944,6 @@ static bool ui_but_menu(bContext *C, uiBut *but)
 	uiPopupMenu *pup;
 	uiLayout *layout;
 	bool is_array, is_array_component;
-	const char *name;
 	uiStringInfo label = {BUT_GET_LABEL, NULL};
 
 /*	if ((but->rnapoin.data && but->rnaprop) == 0 && but->optype == NULL)*/
@@ -4957,12 +4956,11 @@ static bool ui_but_menu(bContext *C, uiBut *but)
 	
 	button_timers_tooltip_remove(C, but);
 
+	/* highly unlikely getting the label ever fails */
 	uiButGetStrInfo(C, but, &label, NULL);
-	name = label.strinfo;
 
-	pup = uiPupMenuBegin(C, name, ICON_NONE);
+	pup = uiPupMenuBegin(C, label.strinfo ? label.strinfo : "", ICON_NONE);
 	layout = uiPupMenuLayout(pup);
-
 	if (label.strinfo)
 		MEM_freeN(label.strinfo);
 

source/blender/editors/interface/interface_regions.c

@@ -2542,7 +2542,7 @@ uiPopupMenu *uiPupMenuBegin(bContext *C, const char *title, int icon)
 	pup->block->handle = MEM_callocN(sizeof(uiPopupBlockHandle), "uiPopupBlockHandle");
 	
 	/* create title button */
-	if (title && title[0]) {
+	if (title[0]) {
 		char titlestr[256];
 		
 		if (icon) {