{:L~} can generate \mathrm{μ} which becomes blank when latex compiled

[doronbehar]

Here's a test case:

import pint
ureg = pint.UnitRegistry()

x = (1e-6 * ureg.meter).to_compact()
latex = "${:L~}$\n".format(x)
print("trying to compile latex code {}".format(latex))
with open("x.tex", "w") as xf:
    xf.write("\\documentclass{minimal}\n")
    xf.write("\\begin{document}\n")
    xf.write(latex)
    xf.write("\\end{document}\n")

import os
os.popen("pdflatex x.tex")

Note the unicode µ in what it prints when you run it, and how it compiles:

Whereas if I simply add a .replace("µ", "\\mu ") I get:

Which is better of course, but I guess not ideal, because the font is italic. I wonder if we should simply apply the above .replace here:

diff --git i/pint/delegates/formatter/latex.py w/pint/delegates/formatter/latex.py
index 476997b..84f05ac 100644
--- i/pint/delegates/formatter/latex.py
+++ w/pint/delegates/formatter/latex.py
@@ -198,8 +198,8 @@ class LatexFormatter(BaseFormatter):
             registry=self._registry,
         )
 
-        numerator = ((rf"\mathrm{{{latex_escape(u)}}}", p) for u, p in numerator)
-        denominator = ((rf"\mathrm{{{latex_escape(u)}}}", p) for u, p in denominator)
+        numerator = ((rf"\mathrm{{{latex_escape(u)}}}".replace("µ", "\\mu "), p) for u, p in numerator)
+        denominator = ((rf"\mathrm{{{latex_escape(u)}}}".replace("µ", "\\mu "), p) for u, p in denominator)
 
         # Localized latex
         # if babel_kwds.get("locale", None):