Fix displaying eval errors in jobset eval view

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)

src/root/eval-error.tt

@@ -13,12 +13,12 @@
 
     <div class="tab-content tab-pane">
         <div id="tabs-errors" class="">
-          [% IF jobset %]
-              <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(jobset.errortime || jobset.lastcheckedtime) %].</p>
-              <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(jobset.fetcherrormsg || jobset.errormsg) %]</pre></div></div>
-          [% ELSIF eval %]
+          [% IF eval %]
               <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(eval.evaluationerror.errortime || eval.timestamp) %].</p>
               <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(eval.evaluationerror.errormsg) %]</pre></div></div>
+          [% ELSIF jobset %]
+              <p>Errors occurred at [% INCLUDE renderDateTime timestamp=(jobset.errortime || jobset.lastcheckedtime) %].</p>
+              <div class="card bg-light"><div class="card-body"><pre>[% HTML.escape(jobset.fetcherrormsg || jobset.errormsg) %]</pre></div></div>
           [% END %]
         </div>
     </div>