[InfoBarGenerics] avoid possible BSoD if self.servicelist is None

https://www.world-of-satellite.com/showthread.php?66866-Crash-when-trying-to-post-the-EPG&p=541681#post541681

lib/python/Screens/InfoBarGenerics.py

@@ -1784,6 +1784,8 @@ def getBouquetServices(self, bouquet):
 		return services
 
 	def multiServiceEPG(self, type, showBouquet):
+		if not self.servicelist:
+			return
 		def openEPG(open, bouquet, bouquets):
 			if open:
 				bouquet = bouquet or self.servicelist.getRoot()