Fix bug in groupId generation
Fix bug in groupId generation

Previously, if calling createNewGroup with an undefined groupId,
no groupId was generated.

This occurred because no entry for "group" + undefined exists in
localStorage, which caused this code to think undefined was a
valid group id.

Fixed by adding `|| groupId == undefined` to the while clause.
Also decoupled the groupId collision check for clarity.

nrizzio/Signal-Desktop,nrizzio/Signal-Desktop,nrizzio/Signal-Desktop,nrizzio/Signal-Desktop