Graphical glitch for techs with no costs.

[michael]

I have a tech that costs 0 resources and 0 seconds. Basically, it's just a choice that the player makes to unlock one of two sets of champions.

A graphical error occurs for a split second as the tech is added to the queue (for 1 turn?).

​http://i.imgur.com/az3kwCZ.jpg

[sanderd17]

In 14459:

fix division by zero for zero-time technologies. Fixes #2334

[Freagarach]

In 26089:

Fix training/researching with zero time.

(Re)introduced in r26000 / rP26000.
Reported by: @wowgetoffyourcellphone
Differential revision: ​https://code.wildfiregames.com/D4378
Reviewed by: @Silier
Refs. #2334