[PATCH] pppoe: handle service string empty case

["Vitja Makarov" <vitja makarov gmail com>]

rp-pppoe could be started with empty service string, this fixes the case.

Index: src/ppp-manager/nm-ppp-manager.c
===================================================================
--- src/ppp-manager/nm-ppp-manager.c	(revision 3521)
+++ src/ppp-manager/nm-ppp-manager.c	(working copy)
@@ -509,7 +509,7 @@
 		nm_cmd_line_add_string (cmd, dev_str);
 		g_free (dev_str);

-		if (pppoe->service) {
+		if (pppoe->service && *pppoe->service) {
 			nm_cmd_line_add_string (cmd, "rp_pppoe_service");
 			nm_cmd_line_add_string (cmd, pppoe->service);
 		}