Hello dropbear - the game was updated to 0.19 this morning, hence your game being terminated. The update to 0.19 was originally scheduled for tomorrow, but brought forward to today. We apologise for the short notice and the inconvenience caused.
The good news is that with this update those pesky upgrade quests have now been taught to recognise when upgrades complete, and so should not cause any further trouble
You can read the full release notes
here and give us your feedback on the update
here