diff -rupN podofo-0.9.6/tools/podofocrop/podofocrop.cpp podofo-0.9.6-new/tools/podofocrop/podofocrop.cpp
--- podofo-0.9.6/tools/podofocrop/podofocrop.cpp	2016-11-18 20:08:56.000000000 +0100
+++ podofo-0.9.6-new/tools/podofocrop/podofocrop.cpp	2019-03-13 23:15:12.352138694 +0100
@@ -61,6 +61,11 @@ void crop_page( PdfPage* pPage, const Pd
            rCropBox.GetHeight());
     */
     rCropBox.ToVariant( var );
+    if (!pPage)
+    {
+        PODOFO_RAISE_ERROR_INFO( ePdfError_InvalidHandle,
+                                "crop_page: No page pointer given" );
+    }
     pPage->GetObject()->GetDictionary().AddKey( PdfName("MediaBox"), var );
 }