Fix Regression: Incomplete file loading is seen for multi page pdf files.
Fix Regression: Incomplete file loading is seen for multi page pdf files.

This was introduced at PDFium revision 12a9940. There was a subtle logic
change for null |parray|.

BUG=415438
R=jun_fang@foxitsoftware.com

Review URL: https://codereview.chromium.org/579363002

DrAlexx/pdfium,bradh/pdfium,bradh/pdfium,bradh/pdfium,nathanstitt/pdfium,witwall/pdfium,azunite/pdf_clone,andoma/pdfium,azunite/pdf_clone,was4444/pdfium,nathanstitt/pdfium,DrAlexx/pdfium,azunite/pdf_clone,duanhjlt/pdfium,pwaller/pdfium,azunite/libpdfium,witwall/pdfium,csharpengineer/pdfium-code,shifucun/pdfium,duanhjlt/pdfium,rouault/pdfium,klokantech/pdfium,andoma/pdfium,chenjian-rits/HelloWorld,shifucun/pdfium,duanhjlt/pdfium,shifucun/pdfium,wwxxyx/pdfium0,azunite/libpdfium,azunite/libpdfium,wwxxyx/pdfium0,DrAlexx/pdfium,rouault/pdfium,witwall/pdfium,ttyangf/PDFium-,wwxxyx/pdfium0,duanhjlt/pdfium,azunite/pdfium_ch,chenjian-rits/HelloWorld,pwaller/pdfium,klokantech/pdfium,rouault/pdfium,andoma/pdfium,nathanstitt/pdfium,azunite/pdfium_ch,was4444/pdfium,pwaller/pdfium,andoma/pdfium,csharpengineer/pdfium-code,ttyangf/PDFium-,DrAlexx/pdfium,was4444/pdfium,csharpengineer/pdfium-code,azunite/pdfium_ch,ttyangf/PDFium-,klokantech/pdfium,azunite/libpdfium,was4444/pdfium,chenjian-rits/HelloWorld