Unable to navigate through input history when message ends with "@" usernames

[jupjohn]

Checklist

• I'm reporting a problem with Chatterino
• I've verified that I'm running the most recent nightly build or stable release
• I've looked for my problem on the wiki
• I've searched the issues and pull requests for similar looking reports

Describe your issue

When navigating through input history with the arrow keys, messages ending in @usernames without a trailing space hijack the navigation.

This doesn't occur when normally tab/return-completing usernames - instead the automatically added space has to be removed (usually by moving the cursor elsewhere in the message and pressing return)

Screenshots

Chatterino2_InputHistoryNavigation_UsernameCompletionHijack.mp4

OS and Chatterino Version

Chatterino 2.5.0 (commit 58a930d) built with Qt 6.7.0 Running on Arch Linux, kernel: 6.8.7-zen1-1-zen