sw unit test: layout dump must be resetted in 'reload' method

Otherwise tests relying on layout dumps will parse the wrong dump.

Change-Id: Ib7b4bc3a231eb3082567a1d1ed38c96835d43add
Reviewed-on: https://gerrit.libreoffice.org/1643Reviewed-by: Noel Power <noel.power@suse.com>
Tested-by: Noel Power <noel.power@suse.com>

sw/qa/extras/inc/swmodeltestbase.hxx

@@ -251,6 +251,11 @@ protected:
         uno::Reference<lang::XComponent> xComponent(xStorable, uno::UNO_QUERY);
         xComponent->dispose();
         mxComponent = loadFromDesktop(aTempFile.GetURL());
+        if (mpXmlBuffer)
+        {
+            xmlBufferFree(mpXmlBuffer);
+            mpXmlBuffer = 0;
+        }
     }
 
     void finish()