fix: android musicxml compatibility

[Danielku15]

Issues

Fixes #2630

Proposed changes

Fixes following problems:

• In some empty rendering cases we had null reference accesses (score null on initial empty render)
• We tried to place dots for hidden notes leading to access to unregistered note steps
• We were not calculating the tuplet digits correctly for any tuplets >19

Checklist

• I consent that this change becomes part of alphaTab under it's current or any future open source license
• Changes are implemented
• New tests were added

Further details

• This is a breaking change
• This change will require update of the documentation/website