fix build without patched Qt

This was broken since 96b03ae078b36122c48ec0ce9b164a24627c5312.

src/lib/multipageloader.cc

@@ -213,10 +213,11 @@ ResourceObject::ResourceObject(MultiPageLoaderPrivate & mpl, const QUrl & u, con
 	}
 
 	webPage.setNetworkAccessManager(&networkAccessManager);
-
+#ifdef __EXTENSIVE_WKHTMLTOPDF_QT_HACK__
 	double devicePixelRatio = multiPageLoader.dpi / 96.; // The used version of WebKit always renders at 96 DPI when no zoom is applied. It does not fully support a device pixel ratio != 1 natively.
 	webPage.mainFrame()->setZoomFactor(devicePixelRatio * settings.zoomFactor); // Zoom in the page to achieve a higher DPI.
 	webPage.setDevicePixelRatio(devicePixelRatio); // Fix CSS media queries (does not affect anything else).
+#endif
 }
 
 /*!