errors leave task running

[leoscholl]

if something happens during a task and it stops unexpectedly, the interface won't let you run another task because the previous one is still running

on windows 10 steps to reproduce:

• create a new manual cursor task
• enter nonsense for one of the parameters (e.g. "q" for reward time)
• press start

[leoscholl]

pretty sure these are windows-specific bugs

[leoscholl]

6be70db35503dc07102c0c7fea6c9a3c461b9c63 fixes this

[leoscholl]

this is happening again

[leoscholl]

got fixed at some point, probably specific to certain errors.