(CONFIRMED) [Bug] Missing specialists

Here's a series of screen shots from the same city, same turn, and needless to say the same game.

Picture 1:
Here's city of Xian with 20 population. 16 of them are working in the field, 4 of them are specialists. Plus the free specialist provided by the Eiffel Tower, there's a total of 5 specialists.

Picture 2:
Now I click the "-" buttom to remove the engineers, merchant and priest. So all the five specialists are now Citizens.

Picture 3:
Then I click the "-" buttom beside the citizens, for four times. Guess what? Just one citizen remains, and the rest simply disappear!

Picture 4:
One more try: click the "-" buttom beside the citizens for the fifth time. Now the city manager turned the citizen an engineer. In another word, a total of 4 specialists disaapeared!

My guess is that the 4 unworkable tiles of the city somehow "devoured" the poor specialist. The save file is available for check.

Same thing happens in aachen as well, but I notice that it returns all the citizens the next turn, and assigns them as specialists before calculating production - so it doesn't actually 'cost' anything.

Bug Description
When you have a population that is larger than the number of workable tiles in a city, clicking 'remove' for citizens makes the citizen disappear - completely (except for free specialists).

Expected behavior
If a citizen can't be assigned to a plot, then clicking '-' should convert the citizen to a specialist.

Actual behavior
The citizen is 'lost' (along with its production bonus etc), although it reappears next turn, and the production bonuses are correctly added.

Steps to reproduce.

1. Download the save from this post, and open it.
2. Scroll to Xian (north of the continent), and open it.
3. Click '-' on each specialist to convert it to a citizen.
4. Click '-' on each citizen, and observe that it disappears.

This would happen on warlords too. It should be fixed if you click add a specialist or click on an unworked tile as well.