[BUG] sang session id, if intentionally corrupted, leads to infinite recursion

[rtshkmr]

replication steps:

1. load page normally at /explore
2. refresh and see no issues
3. inspect to see stored session id (for sanghsession)
4. replace the id to use illegal char (non-hex) e.g. z can be used as the first char
5. observe that the reinit of session is attempted infinitely and the VM's space will run out.

while this is a catastrophic bug, it can only happen now if a user manually modifies the id via devtools, so this bug is unlikely to present itself easily. Hence the lift and priority tags for this.