Tabs without groups

[matthijskooijman]

It seems it is possible to get tabs without groups, in which case they become completely inaccessible (AFAICS).

I've seen this on two occasions:

• I closed a tab group, then used "Undo close tab" to reopen them.
• I restarted Firefox, and opened new tabs before selecting a tab group (at least that's what I think happened).

Would it make sense to have a special "ungrouped" selection (which could be active automatically when ungrouped tabs are present)?