patch 8.1.0577: tabpage right-click menu never shows "Close tab"

Problem:    Tabpage right-click menu never shows "Close tab".
Solution:   Always create the "Close tab" item but ignore the event if there
            is only one tab.
diff --git a/src/gui_mac.c b/src/gui_mac.c
index 96f04c5..ec8ec3a 100644
--- a/src/gui_mac.c
+++ b/src/gui_mac.c
@@ -6705,8 +6705,7 @@
 
     // create tabline popup menu required by vim docs (see :he tabline-menu)
     CreateNewMenu(kTabContextMenuId, 0, &contextMenu);
-    if (first_tabpage->tp_next != NULL)
-	AppendMenuItemTextWithCFString(contextMenu, CFSTR("Close Tab"), 0,
+    AppendMenuItemTextWithCFString(contextMenu, CFSTR("Close Tab"), 0,
 						    TABLINE_MENU_CLOSE, NULL);
     AppendMenuItemTextWithCFString(contextMenu, CFSTR("New Tab"), 0,
 						      TABLINE_MENU_NEW, NULL);