patch 9.0.0343: ColorScheme autocommand triggered when colorscheme not found

Problem:    ColorScheme autocommand triggered when colorscheme is not found.
            (Romain Lafourcade)
Solution:   Only trigger ColorScheme when loading the colorscheme succeeds.
            (closes #11024)
diff --git a/src/highlight.c b/src/highlight.c
index 95cdb46..303d5c2 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -507,7 +507,9 @@
 	sprintf((char *)buf, "colors/%s.vim", name);
 	retval = source_runtime(buf, DIP_START + DIP_OPT);
 	vim_free(buf);
-	apply_autocmds(EVENT_COLORSCHEME, name, curbuf->b_fname, FALSE, curbuf);
+	if (retval == OK)
+	    apply_autocmds(EVENT_COLORSCHEME, name, curbuf->b_fname,
+								FALSE, curbuf);
     }
     recursive = FALSE;