some unit tests not valid when the pdfimport feature is disabled

Change-Id: I2c9aadb292f8c634cff57bf6171be621b6b58064
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/184448
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

sc/qa/extras/scpdfexport.cxx

@@ -222,6 +222,12 @@ void ScPDFExportTest::testMediaShapeScreen_Tdf159094()
 
 void ScPDFExportTest::testPopupRectangleSize_Tdf162955()
 {
+    std::shared_ptr<vcl::pdf::PDFium> pPDFium = vcl::pdf::PDFiumLibrary::get();
+    if (!pPDFium)
+    {
+        return;
+    }
+
     loadFromFile(u"tdf162955_comment.ods");
     uno::Reference<frame::XModel> xModel(mxComponent, uno::UNO_QUERY);