Fix `getBookmark` bug
Fix `getBookmark` bug

I've been banging my head against 'can't read property inlineContent of undefined' for a while and I think I may have found the culprit. It seems `between` expects a `ResolvedPos` but here `getBookmark` was passing the number instead.  This was being fired by `prosemirror-history`. I think this slipped under the radar because it's looks like it only fires in certain history grouping scenarios cases but even then I'm surprised this hasn't surfaced earlier so am a bit confused! Either way, it fixes a couple of tests I've been struggling with.

FIX: Fixes a bug in the default implementation of `Selection.getBookmark`.
ProseMirror/prosemirror-state