Inkscape 1.0rc1 (09960d6, 2020-04-09): Jessyink not working

Hi, I installed the 1.0rc1 (09960d6, 2020-04-09), via zip file. Tried launching the Install/update command of JessyInk and I get the following warning after clicking the Apply button:

jessyInk_install.py:40: ResourceWarning: unclosed file <_io.TextIOWrapper name='jessyInk.js' mode='r' encoding='cp1252'>
  script_elem.text = open(os.path.join(os.path.dirname(__file__), "jessyInk.js")).read()
ResourceWarning: Enable tracemalloc to get the object allocation traceback

JessyInk seems to be installed nevertheless.

However, as soon as I add an Effect, I get the following error:

Traceback (most recent call last):
  File "jessyInk_effects.py", line 67, in <module>
    JessyinkEffects().run()
  File "C:\ProgramData\inkscapebeta\share\inkscape\extensions\inkex\base.py", line 123, in run
    self.save_raw(self.effect())
  File "jessyInk_effects.py", line 48, in effect
    node.set("{" + NSS["jessyink"] + "}effectIn","name:" + self.options.effectIn  + ";order:" + self.options.effectInOrder + ";length:" + str(int(self.options.effectInDuration * 1000)))
TypeError: can only concatenate str (not "int") to str

And even if I try Update afterwards, opening the SVG in the browser I see that the effect is not working. Note that my browser (Firefox) correctly shows SVG files with JessyInk effects created with Inkscape 0.92.4, so I don't think it's the browser's fault.

Inkscape Version and Operating System:

• Inkscape Version: 1.0rc1 (09960d6, 2020-04-09)
• Operating System: Windows 7 32-bit