[iOS] Quote / code block indentation / font can break when backspacing then writing again

[aringenbach]

Steps to reproduce

1. Create quote / code block
2. Type "Text"
3. Backspace until field is empty but don't clear the quote / code block element (e.g: backspace x4)
4. Type something again

Output

Indentation is wrong, and for code block font is not monospaced anymore. This is due to the same issue described in #829

Additional note

This also occurs if we have text preceding the quote / code block with the addition of also losing the background.