fix(pdfx): guard rawDocumentProgress against NaN/Infinity in PdfViewPinch

[MarkianUchiha]

Problem

PdfViewPinch crashes on Android with:

UnsupportedError: Unsupported operation: Infinity or NaN toInt
  at double.round (dart:core-patch/double.dart:196:34)
  at _PdfViewPinchState._determinePagesToShow
    (package:pdfx/src/viewer/pinch/pdf_view_pinch.dart:299:52)

Reproduced on pdfx 2.9.2, Pixel 10a running Android 15/16/17 (edge-to-edge / gesture nav).

Root cause

In _determinePagesToShow, rawDocumentProgress is computed as:

final rawDocumentProgress =
    ((exposed.bottom / r - _lastViewSize!.height) /
        (_docSize!.height - _lastViewSize!.height));

When the document fits exactly in the viewport (or both dimensions are still 0 during the first frame on Android edge-to-edge), the divisor is 0 → produces NaN/Infinity → .round().toInt() throws UnsupportedError and the PDF stays blank.

Fix

Normalize rawDocumentProgress to 0.0 when it is NaN or Infinite before calling .round(). When the document fits the viewport there is no scroll progress to report — 0.0 is the correct semantic value.

var rawDocumentProgress =
    ((exposed.bottom / r - _lastViewSize!.height) /
        (_docSize!.height - _lastViewSize!.height));
if (rawDocumentProgress.isNaN || rawDocumentProgress.isInfinite) {
  rawDocumentProgress = 0.0;
}

Notes

• Same fix as pdfx: fix error if rawDocumentProgress is NaN #602 (thanks @akiller) — opening a new PR from a fresh fork in case pdfx: fix error if rawDocumentProgress is NaN #602 is stalled.
• Verified in a release build on Pixel 10a Android 17 (API 37) targeting production: multiple PDFs open, pinch-zoom works, no more crashes in logcat.
• Change is platform-agnostic; iOS/desktop are unaffected.