Opening an unsupported mime file freezes the UI

Describe the bug

Opening an unsupported mime file from the file view freeze on the wait icon, with no error message displayed to the user

To Reproduce

Run the following in console while browsing files:

OCA.Viewer.open({path:'/path/to/unuspported-mime.type'})

The console reports:

Viewer.vue:450 TypeError: Cannot read properties of undefined (reading 'theme')
    at Viewer.vue:399:1
    at u (runtime.js:63:40)
    at Generator._invoke (runtime.js:294:22)
    at Generator.next (runtime.js:119:21)
    at Vm (Download.vue?b226:19:33)
    at i (Download.vue?b226:19:33)

Probable fix

Seems that in Viewer.vue - https://github.com/nextcloud/viewer/blame/22e47429df029eeb2f36e2361f49e59768dec725/src/views/Viewer.vue#L559 , the use of the handler variable should be swapped with its verification:

			this.theme = handler.theme ?? 'dark'               // Moving that after the if to bring back error message 
			// if we don't have a handler for this mime, abort
			if (!handler) {
				logger.error('The following file could not be displayed', { fileInfo })
				showError(t('viewer', 'There is no plugin available to display this file type'))
				this.close()
				return
			}

Start in src/views/Viewer.vue around the handler check identified in the issue, then reproduce the problem with OCA.Viewer.open({path:'/path/to/unuspported-mime.type'}) while browsing files. Verify that an unsupported MIME type no longer causes the UI to freeze and instead displays the reported error message and closes the viewer.