"Load" button triggers error "Could not reach the API: Precondition Failed" if a leading or trailing space is in the filename box

[taniwallach]

I just build the container using the current master (is at commit 30d3526).

I tried to load:

• Library/SDSU/Discrete/IntegersAndRationals/basemulttableB5.pg
  and got the error message:

Could not reach the API: Precondition Failed

It took me some time to realize that the issue was that there was a training space in the filename box.

I recommend stripping leading/trailing whitespace from the box (on the client side) before running the Load routine.