Descriptive Problem Summary:
https://i.imgur.com/khfwDUT.gif
https://user-images.githubusercontent.com/64715958/ 86698253-ff3df580-bfc3-11ea-9663-b4e900bd6991.gif

Cursor flickers whenever you type something into the chat bar / a say window, and also when you receive a chat message.

only happens when dream seeker is focused. if you tab out to/click on a different program and hover your mouse over dream seeker, the blinking stops till you tab back in.

also noticed when it was happens that the cursor would also disappear after hovering over a context menu (right clicking a turf.) this is fixed by restarting the client.

Additional reports here:
https://github.com/tgstation/tgstation/issues/51970

latest byond (513.1526)
windows 10 pro x64, latest build (1909 / 18363.900)
latest IE (11.900.18362.0), latest edge (83.0.478.58)


Numbered Steps to Reproduce Problem:
type in a say window / chat bar

alternative:
have dreem seeker focused while a chat message is received.

Code Snippet (if applicable) to Reproduce Problem:
N/A - tgstation master

Expected Results:
The cursor doesn't flicker

Actual Results:
The cursor flickers

Does the problem occur:
Every time? Or how often?
Always.
In other games?
Yes, also tested on Rise of the Pirates and confirmed to be happening there as well.
In other user accounts?
Yes
On other computers?
Yes

When does the problem NOT occur?
N/A

Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? (Visit http://www.byond.com/download/build to download old versions for testing.)
Yes. Didn't have this problem on 512 builds. Will test further to see if it started after a specific 513 build.