[ic] Could not eval 'HASH()' from session dbm

[Grant]

I'm on 5.7.6 and I just noticed a blank page when browsing my site.
The global error.log says (hashref removed):

Died in server spawn: Could not eval 'HASH()' from session dbm:
(in cleanup) Can't use an undefined value as a symbol reference at
/path/to/ic/lib/Vend/SessionFile.pm line 147.

Does anyone know how to prevent this?

- Grant