Sony Z Ultra Google Play Edition Crash when Uninstalling
You are not alone. Inability to uninstall any apps and crashes in Settings, are some of the nasty bugs in Sony's recent Google Play edition devices. Currently there are no workarounds, and you must wait until Sony releases an update with fixes for these issues.

Sources: Android Authority, Android Community

[Edit]
Allegedly, the upcoming 4.4.2 OTA update will fix most of the glaring issues.

[Edit 2]
Confirmed, the just released 4.4.2 OTA update fixes those nasty bugs on the Z Ultra.  Check to see if you have it (keep in mind it's probably a staged roll-out, so you might not see the update immediately.)