Merge branch 'viewer-fix' into 'v0.9.3'

Added support for visualizing structures without a unit cell, fixed issue in the viewer not clearing out data from a previous visualization.

See merge request !203
8 jobs for v0.9.3 in 22 minutes and 51 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build #1199086

00:10:26

 
  Test
passed dev_setup_tests #1199091

00:10:56

passed gui_linting #1199088

00:02:30

passed install_tests #1199090

00:08:19

passed linting #1199087

00:06:07

passed tests #1199089

00:12:24

78.0%
 
  Deploy
manual deploy #1199092
allowed to fail manual
 
  Release
manual release #1199093
allowed to fail manual