Unnecessary @u_str characters

[syroezhkin]

The issue

If you use regular numbers in combination with Unitful inside an expression, then unnecessary @u_str characters appear in Pluto:

How to reproduce

using Unitful, Latexify, UnitfulLatexify;

begin
    a = 2u"m"
    @latexdefine c = sqrt(a^2 + 5u"m"^2)
end

[gustaphe]

You need to evaluate 5u"m" before latexifying:
@latexify sqrt(a^2 + $(5u"m")^2).

I agree this is a bit inconvenient, but it's a result of how macros work.