Edit svg font with missing horiz-adv-x

[EllenWasbo]

I was converting a ttf fot to svg using FontForge and when trying to edit this using the Custom Stroke Font - Edit Font it failed and I got nothing. It turned out that there was quite a few glyphs in the svg from FontForge missing the horiz-adv-x attribute. I guess this is a bug in while FontForge generate svg-font (the left/right bearings of those glyphs look fine when inspecting them in FontForge). Anyway - this problem was fixed by changing line 114 of stroke_font_manager.py

From
rOffset = float(e.getAttribute(xROff))

To
if e.getAttribute(xROff) == "":
rOffset = 0
else:
rOffset = float(e.getAttribute(xROff))

Ideally there should be a warning in the end that some (ideally which) glyphs had missing horiz-adv-x and that this is set to 0, or it could be set to the width of the bounding box to have something that might work - not as strange and obviously wrong as 0.

At least this made it possible to continue editing the font. So I'm happy with this solution.