Fix crash when project has no groups and project OWS name equals to

... first layer short name

Author: elpaso

src/server/services/wms/qgswmsrendercontext.cpp

@@ -167,9 +167,19 @@ QStringList QgsWmsRenderContext::flattenedQueryLayers() const
     QStringList _result;
     if ( mLayerGroups.contains( name ) )
     {
-      for ( const auto &l : mLayerGroups[ name ] )
+      const auto &layers  { mLayerGroups[ name ] };
+      for ( const auto &l : layers )
       {
-        _result.append( findLeaves( l->shortName().isEmpty() ? l->name() : l->shortName() ) );
+        const auto nick { layerNickname( *l ) };
+        // This handles the case for root (fake) group
+        if ( mLayerGroups.contains( nick ) )
+        {
+          _result.append( name );
+        }
+        else
+        {
+          _result.append( findLeaves( nick ) );
+        }
       }
     }
     else
@@ -178,7 +188,8 @@ QStringList QgsWmsRenderContext::flattenedQueryLayers() const
     }
     return _result;
   };
-  for ( const auto &name : mParameters.queryLayersNickname() )
+  const auto constNicks { mParameters.queryLayersNickname() };
+  for ( const auto &name : constNicks )
   {
     result.append( findLeaves( name ) );
   }