[EPGRefresh] Fix a frequent crash

EPGRefresh crashed the whole E2 if the scan list contained "orphaned" services.

Root cause 1: The left hand (EPGRefresh) does not know what the right hand is doing (Deleting services that went offline from bouquets).<br>
Root cause 2: Actually the crash was happening inside a check obviously meant to catch this condition, but ironically it's one of the cases where Python prefers to crash rather than to return False.<br>
<br>
In-between cause: Actually EPGRefresh should just auto-remove services that are no longer present.

epgrefresh/src/EPGRefresh.py

@@ -212,9 +212,15 @@ def addServices(self, fromList, toList, channelIds):
 			service = eServiceReference(scanservice.sref)
 			if (service.flags & eServiceReference.isGroup):
 				service = getBestPlayableServiceReference(eServiceReference(scanservice.sref), eServiceReference())
-			if not service.valid() \
-				or (service.flags & (eServiceReference.isMarker|eServiceReference.isDirectory)):
 
+			# service can be a "NoneType" without attribute "valid" -> Crash
+			try:
+				if not service.valid():
+					continue
+			except:
+				continue
+
+			if (service.flags & (eServiceReference.isMarker|eServiceReference.isDirectory)):
 				continue
 
 			channelID = '%08x%04x%04x' % (