[MM-18369] Fixed issue where no transition on RHS broke searching on Firefox

[devinbinnie]

Summary

My fix here #3594 caused an issue with Firefox, since Firefox does not provide a default computed value for transitions like Chrome does. This PR checks to make sure there is a transition and that it's not the default value. Tested with Chrome, Firefox, Safari and Edge.

Ticket Link

https://mattermost.atlassian.net/browse/MM-18369

[lindy65]

Thanks @devinbinnie!

I've tested on Firefox and Search is working without showing any 'searching' spinner.

I have, however, found an issue where, while using the "in:~channel" search, the channel I'm typing into the Search box becomes bolded in the left-hand-side channels list.

I've attached a GIF of this happening (sorry, you have to watch right to the end as I was trying to get it to repro and it only repro'd right at the end!). There is no error in the JS console. I'm not sure whether this is caused by / an issue on this PR?

[devinbinnie]

@lindy65 Hmm, weird. Definitely a separate issue though. Can you file a new bug?

[lindy65]

Thanks @devinbinnie, I've filed https://mattermost.atlassian.net/browse/MM-18495 for the bolding of the channel name in the LHS.

Otherwise this PR looks good to me!

Is this something that a unit test can be added for?