Fix stack corruptions in special cases

Issue was caused by wrong array length used
for result of name_uiprefix_id, which shall
actually be 1 byte bugger than MAX_ID_NAME.

Reported by Sebastian Koenig in IRC.

source/blender/editors/interface/interface_layout.c

@@ -1357,6 +1357,7 @@ static void rna_search_cb(const struct bContext *C, void *arg_but, const char *s
 			char name_ui[MAX_ID_NAME];
 
 #if 0       /* this name is used for a string comparison and can't be modified, TODO */
+			/* if ever enabled, make name_ui be MAX_ID_NAME+1 */
 			name_uiprefix_id(name_ui, id);
 #else
 			BLI_strncpy(name_ui, id->name + 2, sizeof(name_ui));

source/blender/editors/interface/interface_templates.c

@@ -151,7 +151,10 @@ static void id_search_cb(const bContext *C, void *arg_template, const char *str,
 					continue;
 
 			if (BLI_strcasestr(id->name + 2, str)) {
-				char name_ui[MAX_ID_NAME];
+				/* +1 is needed because name_uiprefix_id used 3 letter prefix
+				 * followed by ID_NAME-2 characters from id->name
+				 */
+				char name_ui[MAX_ID_NAME + 1];
 				name_uiprefix_id(name_ui, id);
 
 				iconid = ui_id_icon_get((bContext *)C, id, template->preview);