If incremental barcodes are disabled, it is not possible to add an item without a barcode. The system still attempts to generate a barcode along the lines of '1.79769313486232e+309'.
Created attachment 13467 [details] [review] Bug 9090 - Cannot add item without barcode
Created attachment 13468 [details] [review] Bug 9090 - Cannot add item without barcode
Created attachment 13469 [details] [review] Bug 9090 - Cannot add item without barcode
Created attachment 13470 [details] [review] Bug 9090 - Cannot add item without barcode
I think this only happens if you have had incremental on, and then turn it off in the same session. I was unable to replicate this until I turned incremental on, and then off again.
and then, shift-refreshing the page caused the problem to disappear - it appears the bug is related to caching of the autofill javascript?
This does not appear to be a problem in master with the standard sample data. I'll have to do some more digging and see if this is possibly an interaction with other system settings.
Unable to replicate - no reason to have it hanging out there.