More than one heading throws error on copy-paste

[nokola]

Summary

Copy-pasting multiple # headings throws error.

Steps to reproduce

1. Open https://remirror.io/
2. Type aaabbb in editor and position cursor between the aaa and bbb:
   
3. Copy-paste this text from somewhere:

# hello
# world

Expected results

aaa and bbb are separated by two lines that each say "hello" and "world" in heading 1 style.

Actual results

Error in developer console and this as editor:

5060.3acc2677.js:2 Uncaught Error: Called contentMatchAt on a node with invalid content
    at R.contentMatchAt (5060.3acc2677.js:2)
    at _.placeNodes (5060.3acc2677.js:2)
    at _.fit (5060.3acc2677.js:2)
    at 5060.3acc2677.js:2
    at e.u.replace (5060.3acc2677.js:2)
    at e.u.replaceRange (5060.3acc2677.js:2)
    at e.s.replace (5060.3acc2677.js:2)
    at e.replace (5060.3acc2677.js:2)
    at e.replaceSelection (5060.3acc2677.js:2)
    at xe (5060.3acc2677.js:2)

Possible Solution

Looks like issue with prosemirror-paste-rules not being able to paste more than one block node inside inline content.

Screenshot(s)