[0.15.1] Ore field amount stuck to cursor when in tech view

[Hexicube]

As shown, the amount of ore in the previously highlighted ore field does not go away when the technology window is open: http://i.imgur.com/C6HxF2R.png

Reproduction: Mouse over an ore field and press T.

[posila]

Thanks for the report.
Fixed for 0.15.3