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)

Author: brammool

src/gui_w32.c

@@ -127,6 +127,9 @@ gui_mch_set_rendering_options(char_u *s)
 	    return FAIL;
     }
 
+    if (!gui.in_use)
+	return OK;  /* only checking the syntax of the value */
+
     /* Enable DirectX/DirectWrite */
     if (dx_enable)
     {

src/option.c

@@ -7406,7 +7406,7 @@ did_set_string_option(
 
 #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;

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1373,
 /**/
     1372,
 /**/