account: Make stack non-homogeneous

The spinner should be at the center of the view, not the other child of
the stack.
4 jobs for <span class="ref-name">account-ui-fix</span> in 26 minutes and 26 seconds (queued for 1 second)
Status Job ID Name Coverage
  Check
passed #245824
check

00:00:23

 
  Test
passed #245825
flatpak

00:25:00

 
  Review
passed #245826
review

00:00:47

failed #245827
allowed to fail manual
stop_review

00:00:14

 
Name Stage Failure
failed
stop_review Review
Using Docker executor with image fedora:29 ...
Pulling docker image fedora:29 ...
Using docker image sha256:d09302f77cfcc3e867829d80ff47f9e7738ffef69730d54ec44341a9fb1d359b for fedora:29 ...
Running on runner-d836cf30-project-6592-concurrent-0 via gcc150.bak.milne.osuosl.org...
Cloning repository...
Cloning into '/builds/sfanxiang/fractal'...
Checking out bdb4d5c7 as account-ui-fix...
fatal: reference is not a tree: bdb4d5c7af65fcc1c70b0450692052f82f098837
ERROR: Job failed: exit code 1