Simplify the code that resets the value of the `pageNumber` element in `PDFViewerApplication.setInitialView`

After the creation of `PDFViewer`, its `_resetView` method takes care of resetting, among other things, the page number property. Hence we don't need to set `pdfViewer.currentPageNumber = 1;` here any more, and the comment is no longer accurate either.

web/viewer.js

@@ -954,11 +954,10 @@ var PDFViewerApplication = {
   setInitialView: function pdfViewSetInitialView(storedHash, scale) {
     this.isInitialViewSet = true;
 
-    // When opening a new file (when one is already loaded in the viewer):
-    // Reset 'currentPageNumber', since otherwise the page's scale will be wrong
-    // if 'currentPageNumber' is larger than the number of pages in the file.
+    // When opening a new file, when one is already loaded in the viewer,
+    // ensure that the 'pageNumber' element displays the correct value.
     document.getElementById('pageNumber').value =
-      this.pdfViewer.currentPageNumber = 1;
+      this.pdfViewer.currentPageNumber;
 
     if (this.initialDestination) {
       this.pdfLinkService.navigateTo(this.initialDestination);