patch 8.0.1373: no error when settting 'renderoptions' before starting GUI

Problem:    No error when settting 'renderoptions' to an invalid value before
            starting the GUI.
Solution:   Always check the value. (Ken Takata, closes #2413)
diff --git a/src/option.c b/src/option.c
index c97056b..08fb789 100644
--- a/src/option.c
+++ b/src/option.c
@@ -7406,7 +7406,7 @@
 
 #if defined(FEAT_RENDER_OPTIONS)
     /* 'renderoptions' */
-    else if (varp == &p_rop && gui.in_use)
+    else if (varp == &p_rop)
     {
 	if (!gui_mch_set_rendering_options(p_rop))
 	    errmsg = e_invarg;