updated for version 7.3.019
Problem:    ":nbstart" can fail silently.
Solution:   Give an error when netbeans is not supported by the GUI. (Xavier
            de Gaye)
diff --git a/src/netbeans.c b/src/netbeans.c
index f39111d..6f92b3c 100644
--- a/src/netbeans.c
+++ b/src/netbeans.c
@@ -2773,6 +2773,16 @@
 ex_nbstart(eap)
     exarg_T	*eap;
 {
+#ifdef FEAT_GUI
+# if !defined(FEAT_GUI_X11) && !defined(FEAT_GUI_GTK)  \
+                && !defined(FEAT_GUI_W32)
+    if (gui.in_use)
+    {
+        EMSG(_("E838: netbeans is not supported with this GUI"));
+        return;
+    }
+# endif
+#endif
     netbeans_open((char *)eap->arg, FALSE);
 }