[pvr] fix: delete of empty group with an invalid id ends up in deleting the wrong group

[xhaggi]

If your backend holds an empty group and you import the channel groups for the first time (after a clear of the TV database or with a new setup) each of the groups won't hold a valid id because they are new to our database. As we delete empty groups after loading the related channels and these groups don't hold a valid id (-1) this will result in deleting the wrong group e.g. the first group with id -1 which is the internal "All channels" group. After that everything is screwed up.

This will add a check for a valid group id (> 0) to CPVRChannelGroups::DeleteGroup to prevent deleting the wrong group.

@Jalle19 @opdenkamp mind taking a look

[Jalle19]

Sounds reasonable

[xhaggi]

@Jalle19 should i drop the logging?

[xhaggi]

jenkins build this please

[xhaggi]

Instead of return immediately if group don't hold a valid id, I've changed the condition within the iteration. Now it checks for the same instance or if group id is valid (greater 0) for id equality. This will delete the group from the list and if a valid id exists from the database.

[xhaggi]

jenkins build this please

[xhaggi]

@Jalle19 mind taking a quick look again

[Jalle19]

I guess it's okay, only looked at the diff though, not the whole context.