Connection delay of `0` causes unexpected behavior

[jlubo]

Setting the delay time of a connection to0 causes unexpected behavior. Specifically, the probing of variables from mechanisms fails by yielding an empty array (see the code here).

I've encountered the issue on Arbor commit version 2ec4db34bdc67ddb9d2b16b1946ee40d974eb413. According to @thorstenhater, it has not yet been fixed by the currently most recent version (08a157fb52455c3a45b7ffae1bf6aabd33a43023).

The issue can be circumvented by setting the delay to the duration of one timestep. Note that it is related to what is mentioned here.