[MusicXML] <notations> tag causes infinite loop on load

Steps to reproduce: just try opening the attached file.
Remove tag from line 402 and it will work.

Offending bit of code seems to be in
importxmlpass2.cpp in MusicXMLParserPass2::note

under:
// handle the postponed children of
while-loop, where commenting out the code for:
// skip to either start of next child or end of

seems to make things work again. I am reluctant to propose that as a fix here, because that code was probably put there for a good reason, so it likely needs to be reworked rather than removed, but I am not competent to do so.

Tagging major as it causes an infinite loop for completely well-formed xml imput.