Deleting a selection that starts with a blank line in Firefox does not delete the entire section

Was able to reproduce this bug on CAC and Confluence master.

Steps to reproduce:
1. Type a blank line in the editor
2. On the next line, type some text
3. Start selecting from the start of the blank line to the end of the next line
4. Hit delete (on mac)
5. Only the blank line is deleted, the second line of text remains in the editor