patch 8.2.2119: GTK3: status line background color is wrong

Problem:    GTK3: status line background color is wrong.
Solution:   Don't change the code for earlier GTK3 versions. (closes #7444)
diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index 22788e8..ec81d4e 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -4031,15 +4031,18 @@
     void
 gui_mch_new_colors(void)
 {
-    if (gui.formwin != NULL && gtk_widget_get_window(gui.formwin) != NULL)
+    if (gui.drawarea != NULL
+#if GTK_CHECK_VERSION(3,22,2)
+	    && gui.formwin != NULL
+#endif
+	    && gtk_widget_get_window(gui.drawarea) != NULL)
     {
 #if !GTK_CHECK_VERSION(3,22,2)
-	GdkWindow * const da_win = gtk_widget_get_window(gui.formwin);
+	GdkWindow * const da_win = gtk_widget_get_window(gui.drawarea);
 #endif
-
 #if GTK_CHECK_VERSION(3,22,2)
-	GtkStyleContext * const context
-	    = gtk_widget_get_style_context(gui.formwin);
+	GtkStyleContext * const context =
+				     gtk_widget_get_style_context(gui.formwin);
 	GtkCssProvider * const provider = gtk_css_provider_new();
 	gchar * const css = g_strdup_printf(
 		"widget#vim-gtk-form {\n"