Initialize slider with default values before calling initWatchdog()

[maciex]

When the addon is not connected to Kodi, the error appears in the logs when opening the remote page.

Error: cannot call methods on slider prior to initialization; attempted to call method 'value'  jquery-2.1.4.min.js:2:1821
	error moz-extension://3dbca519-d1fb-43d8-979a-dc1b00563750/js/jquery-2.1.4.min.js:2:1821
	e.widget.bridge/e.fn[t]/< moz-extension://3dbca519-d1fb-43d8-979a-dc1b00563750/js/jquery-ui-1.11.4.min.js:6:9073
	each moz-extension://3dbca519-d1fb-43d8-979a-dc1b00563750/js/jquery-2.1.4.min.js:2:2880
	each moz-extension://3dbca519-d1fb-43d8-979a-dc1b00563750/js/jquery-2.1.4.min.js:2:845
	e.widget.bridge/e.fn[t] moz-extension://3dbca519-d1fb-43d8-979a-dc1b00563750/js/jquery-ui-1.11.4.min.js:6:8812
	initWatchdog/watchdog< moz-extension://3dbca519-d1fb-43d8-979a-dc1b00563750/js/remote.js:299:27```