patch 8.1.1595: MS-Windows with VIMDLL: colors wrong in console

Problem:    MS-Windows with VIMDLL: colors wrong in console.
Solution:   Do not set the GUI colors when not using the GUI. (Ken Takata,
            closes #4588)
diff --git a/src/syntax.c b/src/syntax.c
index 756d0ea..8c23d20 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -9554,6 +9554,10 @@
 	at_en.ae_u.cterm.bg_color = sgp->sg_cterm_bg;
 # ifdef FEAT_TERMGUICOLORS
 #  ifdef MSWIN
+#   ifdef VIMDLL
+	// Only when not using the GUI.
+	if (!gui.in_use && !gui.starting)
+#   endif
 	{
 	    int id;
 	    guicolor_T fg, bg;