fix display of uninitialized ports

git-svn-id: svn://svn.openwrt.org/openwrt/branches/buildroot-ng/openwrt@3946 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/switch/src/switch-robo.c

@@ -315,6 +315,8 @@ static int handle_vlan_port_read(void *driver, char *buf, int nr)
 		}
 	}
 
+	buf[len] = '\0';
+
 	return len;
 }