shrewd moon
This happened because apparently if you destroy/demolish Food Storage buildings and undo it while on the destroy/demolish mode, it will reset that Food Storage to 0. If you destroy it fully one more time, it displays a negative number instead.
This is effectively a softlock since restarting the game or leaving the world would not do anything to resolve the issue.
The ONLY way you can fix it is by adding that value back into a positive by using even more Food Storage buildings or resetting the world back to square one.
near wigeon