Fix termgui_mch_get_color in MacVim

src/MacVim/gui_macvim.m

@@ -1563,6 +1563,9 @@ gui_mch_flash(int msec)
     guicolor_T
 gui_mch_get_color(char_u *name)
 {
+    if (![MMBackend sharedInstance])
+	return INVALCOLOR;
+
 #ifdef FEAT_MBYTE
     name = CONVERT_TO_UTF8(name);
 #endif

src/term.c

@@ -1269,6 +1269,12 @@ static struct builtin_term builtin_termcaps[] =
     guicolor_T
 termgui_mch_get_color(char_u *name)
 {
+# if defined(FEAT_GUI_MACVIM)
+    guicolor_T t;
+    t = gui_mch_get_color(name);
+    if (t != INVALCOLOR)
+	return t;
+# endif
     return gui_get_color_cmn(name);
 }