Use isEmpty() instead of getLength()

Change-Id: I2b67c3eebea09d8bebe045ca98341e3347b08fc7
Reviewed-on: https://gerrit.libreoffice.org/45569Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>
(cherry picked from commit 3c7b1779)
Reviewed-on: https://gerrit.libreoffice.org/45676Reviewed-by: Julien Nabet <serval2412@yahoo.fr>

xmloff/source/draw/shapeexport.cxx

@@ -2375,7 +2375,7 @@ void XMLShapeExport::ImpExportGraphicObjectShape(
             {
                 const OUString aStr = mrExport.AddEmbeddedGraphicObject(aReplacementUrl);
 
-                if(aStr.getLength())
+                if(!aStr.isEmpty())
                 {
                     mrExport.AddAttribute(XML_NAMESPACE_XLINK, XML_HREF, aStr);
                     mrExport.AddAttribute(XML_NAMESPACE_XLINK, XML_TYPE, XML_SIMPLE );