Multi-line String creates duplicate string

[ghost]

Operating system or device - Godot version: 2.1

Issue description (what happened, and what was expected):
Alright folks, this is a pretty fascinating bug:

    get_node("RichTextLabel").set_bbcode("""
    hello
    """)

This is valid GDScript syntax, but, it will actually insert 2x hello strings instead of just one.

If you do it without a initial line break:

    get_node("RichTextLabel").set_bbcode("""hello
    """)

It works fine. I am making some extensive tooltips and need the line breaks but it literally duplicated my text, lol pretty funny tbh. I am not sure if this intended :P

[volzhs]

also can reproduce with set_bbcode("\nhello")

[bojidar-bg]

set_bbcode/append_bbcode both do something funny, as evidenced by #3773 (actually, set_bbcode calls append_bbcode through parse_bbcode internally...)

Anyway, seems like this issue is either in the two calls to add_text on lines 1475 and 1485 (probably no) or in add_text itself, specifically the weirdness it does with newlines and similar.

Can you retest with add_line("\nhello") as well?

[volzhs]

@bojidar-bg
same result in both set_bbcode and append_bbcode... and so weird result...

No pre-entered string with RichTextLabel.

[bojidar-bg]

@volzhs Uh my bad, I meant add_text("\nstuff") (and yeah, append_bbcode is expected to fail in the same way).

[volzhs]

@bojidar-bg
add_text result is here.

[bojidar-bg]

Ok, issue location confirmed and also a duplicate of #3773. @godotengine/bugsquad I'm not sure which of the two to close though, since this got much more attention and debugging...