There are two functions cast the line's endpoints to int value for get the unique value. The two functions are
"_determine_number_of_rows_and_columns" and "_determine_table_cell_boundaries". This conversion causes "_is_unbroken" function run error.

I read this part of code. Usually to judging intersection between the lines based on their distance of the line's x / y value.

But the function "_determine_table_cell_boundaries" violate this convention for get the unique value. And then the function "_is_unbroken" use the converted int value.

This will throws an error: "A Rectangle must have a non-negative height" sometimes.

Example:
original:
xs: [110.81, 484.49, 110.81, 484.49, 110.81, 484.49, 111.05, 111.05, 207.35, 207.35, 262.85, 262.85, 315.65, 315.65, 430.25, 430.25, 484.25, 484.25]
ys: [526.19, 526.19, 557.89, 557.89, 647.49, 647.49, 525.95, 647.25, 525.95, 647.25, 525.95, 647.25, 525.95, 647.25, 525.95, 647.25, 525.95, 647.25]

sorted unique
xs: [110, 111, 207, 262, 315, 430, 484]
ys:[525, 526, 557, 647]

In addition, the code "min(l.y0, l.y1) <= r.get_y() and max(l.y0, l.y1) >= r.get_y() + r.get_height()" in function "_is_unbroken", r.get_y() used converted value but l.y0 / l.y1 use the original value. Converted value must <= original value, so the above code will return false aways when l and r has same endpoint.

The commit for fix the problem above.