RangeError: Index 0 out of range for <>

I really can’t find an explanation for this or is this the expected behavior. Please can someone else test it also. I used a clean install and just changed:

content: 'block+'

to

content: 'heading[level=1] block+'

Then to get the out of range error in the console, follow the following steps:

  • Type a heading with some text
  • Hit enter
  • Type a paragraph with some text
  • Select some text of the paragraph with the mouse
  • Hit the “Select parent node” button in the menubar
  • Click on the selected text

The last action triggers the out of range error. Is this expected behavior or might this be a small bug? I’d really like to have it confirmed.