Solution or Workaround
Why do I get the error: "Warning: invalid layer"?
There are 2 reasons this message can occur:
1. The wrong layer type is specified when creating a new layer. For example, if 'line' is specified as the layer type when creating a point layer.
2. The name specified for a new layer already exists in the geo file.
Make sure each layer name is unique and that the layer type is correctly defined.