• I've checked docs and closed issues for possible solutions.
• I can't find my issue in the FAQ.

Describe the bug

There is a function which counts the length of each line as below when i use "Textual" :

def line_structure(content: Text) -> int:
   lines = content.split()
   line_count = []
   for line in lines:
        line_count.append(line.cell_len)
   return line_count

The Text.split() method will call Text.divide() method, in that method, the IndexError may occur in certain situations. It says:" IndexError: list index out of range"

Here are the reasons why this error occurs:
The divide() method comes from the source file text.py in rich as below:
https://github.com/Textualize/rich/blob/68224905f5dc7a3c765e04aba0460b75a95f5004/rich/text.py
The divede() method starts at line #1051 ( to prevent from seeing different positions)

The code that caused the error located at the #1097 or #1113 lines.
For instance, 

while True:
                    line_start, line_end = line_ranges[end_line_no]     #1113 line
                    if span_end < line_start:
                        upper_bound = end_line_no - 1
                    elif span_end > line_end:
                        lower_bound = end_line_no + 1
                    else:
                        break
                    end_line_no = (lower_bound + upper_bound) // 2

When the variable "end_line_no" = line_count = len(line_ranges), it will raise a IndexError.
If span_end > line_end, variable end_line_no may continue to increase until it equals line_count. There is no corresponding restriction to limit the value of end_line_no within the correct range. I don’t know why the value of span_end is greater than end_line, but I can only say that in some cases, at least in my code, it does occur. [The error message provided clearly indicates that the span_end at the time was 104 while the text_length (which equals to end_line) was 100 , sometimes they are other values.]

I have temporarily fixed this problem by adding some codes like

if end_line_no >= line_count:
    end_line_no = line_count - 1
    break

after line #1113 and #1097, and this bug has not occurred again.

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