I tried to paper over this initially so I could get a hotfix out that would stop it from hard crashing all over the place. Now that I've had some time to go looking, I have no idea why the StrangeEgg has hasDynamicProperties set at all - in fact I have no idea why it's setup in the way it is for a bunch of things.
I can't find anywhere it's ever given a non-standard property value during gameplay.
I don't know why it's marked as isUsable, considering its use function is the dummy "I can't do anything with this" - which then hides the drop button in the interface.
It has at least surfaced a minor oversight in my paper-fixes which is what is resulting in the 0quant thing. For any item that was causing a crash, but I couldn't find out where and what dynamic properties were actually important for them, I just made canMergeWith() spit back false - ergo, the item cannot merge with its identical clone, which is how the shop quantities are effectively calculated.