fix bug NaN (divide by zero)

[hnvn]

No description provided.

[vicajilau]

This fixes the same NaN/Infinity crash as #602 and #621, but with a different approach: this version skips the whole progress update when _docSize.height == _lastViewSize.height instead of normalizing rawDocumentProgress to 0.0. That leaves _documentProgress stale in that case rather than explicitly reporting no scroll progress. We'll merge one of #602/#621 (which normalize to 0.0) and close this one as a duplicate with a less precise fix.

[vicajilau]

Following up on the earlier comment: we merged #621, which normalizes the raw progress to 0.0 the same way #602 did, rather than skipping the update. Closing this as a duplicate. Thanks for the fix, and sorry for the delay in following up.