waterfall_plot: tooltips don't work with column names from original dataset

[ASmirnov-HORIS]

Example:

data = {
    'cat': ['A', 'B'],
    'val': [1, 2],
}
waterfall_plot(data, 'cat', 'val', relative_tooltips=layer_tooltips().line("@cat/@..xlabel.."))

throws IllegalArgumentException; expected: