[Project-OWS-Tab] Doen't add null CRS to list

It was possible to add null CRS in the OWS Tab CRS list. To avoid it, I
add a test on return 0 as CRS Id and to set a default CRS with the last
in the OWS Tab CRS list.

src/app/qgsprojectproperties.cpp

@@ -996,7 +996,10 @@ void QgsProjectProperties::on_pbnWMSAddSRS_clicked()
 {
   QgsGenericProjectionSelector *mySelector = new QgsGenericProjectionSelector( this );
   mySelector->setMessage();
-  if ( mySelector->exec() )
+  if ( mWMSList->count() > 0 ) {
+    mySelector->setSelectedAuthId( mWMSList->item( mWMSList->count()-1 )->text() );
+  }
+  if ( mySelector->exec() && mySelector->selectedCrsId()!=0 )
   {
     QString authid = mySelector->selectedAuthId();