Today I started playing around with Casper Signer to detect why it is frequently crashing. First thing I noticed that there are following MobX warnings:

mobx.module.js:3369 [mobx.array] Attempt to read an array index (0) that is out of bounds (0). Please check length first. Out of bound indices will not be tracked by MobX

They appear when you either open Key Management or Connected Sites in hamburger menu.