clear the document information when a plucker document is closed

svn path=/trunk/KDE/kdegraphics/okular/; revision=798897

generators/plucker/generator_plucker.cpp

@@ -120,6 +120,9 @@ bool PluckerGenerator::doCloseDocument()
     qDeleteAll( mPages );
     mPages.clear();
 
+    // do not use clear() for the following, otherwise its type is changed
+    mDocumentInfo = Okular::DocumentInfo();
+
     return true;
 }