Chat Placeholder Style implementation causes chat to break with backspaces on iOS

[GigiaJ]

Describe the bug

Currently, due to how the style is implemented (from my understanding), Webkit (iOS particularly) breaks the chat UI when typing backspace on the virtual keyboard (seems fine on iPadOS with a magic keyboard) a blank message (and I believe it occurs for similar circumstances) in the editor.

Reproduction

Open Cinny on iOS and type backspace immediately.
Editor now only allows input of characters, but can’t use the send button, backspace, enter to send, etc.

Expected behavior

For the chat to not become non-functional after hitting backspace almost arbitrarily into a message.

Platform and versions

1. iOS 18
2. Safari (any webkit browser I imagine) 
   Engine version: 621.2.5
3. Cinny 4.8.0
4. Matrix.org

Additional context

I’ve already written a fix I think. At least it has been working for me.
Just opening this before making a PR as I didn’t notice it elsewhere.