PdfPreview unhandled exception when popped

When route which contains PdfPreview is popped, we got a:
Unhandled Exception: setState() called after dispose()

The solution is to add if (!mounted) return; in the file pdf_preview.dart in the function _raster() just after await for (final PdfRaster page in Printing.raster(_doc, dpi: dpi)) {

@@ -3,6 +3,7 @@
 ## 3.6.0
 
 - Added pdfFileName prop to PdfPreview Widget [Marcos Rodriguez]
+- Fix PdfPreview unhandled exception when popped [computib]
 
 ## 3.5.0
 

@@ -120,6 +120,9 @@ class _PdfPreviewState extends State<PdfPreview> {
 
     var pageNum = 0;
     await for (final PdfRaster page in Printing.raster(_doc, dpi: dpi)) {
+      if (!mounted) {
+        return;
+      }
       setState(() {
         if (pages.length <= pageNum) {
           pages.add(_PdfPreviewPage(