Extension "Text -> Merge" stopped working in alpha 1.0

Steps to reproduce:

• open Inkscape
• create a text, e.g. "Hello World" in a new file
• copy the text
• select both texts
• from the menu, choose "extensions" -> "text" -> "Merge"
• keep all the defaults, click on [Apply]

What happened?

Error message:

text_merge.py:87: DeprecationWarning: Effect.selected is now a dictionary in the svg document. Use self.svg.selected instead.
  x, y, w, h = dimen[self.selected.keys()[0]]
Traceback (most recent call last):
  File "text_merge.py", line 184, in <module>
    Merge().run()
  File "inkex/base.py", line 84, in run
    ret = self.effect()
  File "text_merge.py", line 87, in effect
    x, y, w, h = dimen[self.selected.keys()[0]]
KeyError: 'text12'

What should have happened?

Text should have been converted to Braille

Inkscape Version and Operating System:

• Inkscape Version: 1.0alpha (d7d7b92, 2019-04-16)
• Operating System: Windows
• Operating System version: Windows 7 German Enterprise, Windows 10 Home German