get_character_line reports wrong line in RichTextLabel

[henriquelalves]

Godot version

Master branch [6758a7f]

System information

Manjaro

Issue description

get_character_line returns the wrong line on some characters when Autowrap Mode is not set to "Off". I couldn't understand the source of error, but apparently it happens when the text breaks lines in Autowrap "Arbitrary", or when the text auto-formats to remove extra space characters. The following images shows a case when this error happens:

The problem is obvious on the the last two "c"s that should been on line 4, but instead only the last one is. This offset happened on the second letter "b", that should been line 1 (but it's shown as line 0).

Steps to reproduce

Use a RichText label and set Autowrap mode to any option but "Off". Some texts might have this problem when you query for a character line.

Minimal reproduction project

bug_character_line.zip