Inkscape "copy to clipboard" fails with "invalid literal for float"

Copying objects seems to be broken for a number of string objects in Inkscape 0.91:
I have a text object with manual kerning (imported from a pdf), and it has a
<svg:text> <svg:tspan> with multiple x-attributes separated by spaces.
It won't copy to the clipboard.

Traceback (most recent call last):
  File "ink2canvas.py", line 89, in <module>
    ink.affect()
  File "/usr/share/inkscape/extensions/inkex.py", line 268, in affect
    self.effect()
  File "ink2canvas.py", line 84, in effect
    self.walk_tree(svg_root)
  File "ink2canvas.py", line 75, in walk_tree
    self.walk_tree(node)
  File "ink2canvas.py", line 75, in walk_tree
    self.walk_tree(node)
  File "ink2canvas.py", line 74, in walk_tree
    elem.draw()
  File "/usr/share/inkscape/extensions/ink2canvas/svg.py", line 371, in draw
    _x = float(tspan.get("x"))
ValueError: invalid literal for float(): -7.6668 -2.1068001 3.7332001 9.2931995 12.0732 17.6332 23.193199 28.753201 34.313202 39.873199 45.433201

Similarly, I have another text object imported from pdf, which contains an en-dash character.
This also fails to copy to the clipboard.

Traceback (most recent call last):
  File "ink2canvas.py", line 89, in <module>
    ink.affect()
  File "/usr/share/inkscape/extensions/inkex.py", line 269, in affect
    if output: self.output()
  File "ink2canvas.py", line 34, in output
    sys.stdout.write(self.canvas.output())
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2212' in position 361: ordinal not in range(128)

I am running on Ubuntu 14.04 64-bit, gnome classic / metacity.