Issue description
When trying to reduce the emptying threshold, clicking on the red flag causes it to immediately jump to 0 with no way to drag it back to a higher value. I have only tried this on small storage as it is a new map but it impacts all 3 types.
Reproduction steps
Build a storage, assign a product and try to reduce the emptying threshold to less than full but greater than 0.
Game version and build number
v0.7.1e b424
Operating system
Windows
