patch 8.2.2500: build fails without the GUI feature

Problem:    Build fails without the GUI feature.
Solution:   Add #ifdef.
diff --git a/src/main.c b/src/main.c
index 82e89a8..76252c7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1979,7 +1979,9 @@
 		{
 		    Columns = 80;	// need to init Columns
 		    info_message = TRUE; // use mch_msg(), not mch_errmsg()
+#if defined(FEAT_GUI) && !defined(ALWAYS_USE_GUI)
 		    gui.starting = FALSE; // not starting GUI, will exit
+#endif
 		    list_version();
 		    msg_putchar('\n');
 		    msg_didout = FALSE;