Plotting grids with empty id field for nodes causes error

[danielfeismann]

see OsmoGrid#433 for details

File ~\PycharmProjects\pypsdm\pypsdm\plots\grid.py:165, in _add_node_trace.<locals>.to_hover_text(node_data)
    159 if node_data.name not in node_hover_data:
    160     raise ValueError(
    161         f"Node with uuid: {node_data.name} not found in node_hover_data"
    162     )
    164 return (
--> 165     node_data["id"]
    166     + "<br>"
    167     + node_data.name
    168     + "<br>"
    169     + "<br>".join(
    170         [
    171             f"{key}={value}"
    172             for key, value in node_hover_data[node_data.name].items()
    173         ]
    174     )
    175 )

TypeError: unsupported operand type(s) for +: 'float' and 'str'