Quickfix for something that annoyed me once too often.
Specifically, I'm talking about `/eval/1#tabs-errors`.
To not fetch long errors on each request, this is only done on-demand.
I.e., when the tab is opened, an iframe is requested with the errors.
This iframe uses a template for both the jobset view and the jobset-eval
view. It is differentiated by checking if `jobset` or `eval` is defined.
However, the jobset-eval view also has a `jobset` variable in its stash
which means that in both cases the `if` path was used. Since
`jobset.fetcherrormsg` isn't defined in the eval case though, you always
got an empty error.
The band-aid fix is relatively simple: swap if and else: the `eval`
variable is not defined in the stash of the jobset view, so now this is
a useful condition to decide which view we're in.
(cherry picked from commit 70c3d75f73)
