added cleanup for number_convert to address errors

[fastflair]

Description

The Insider.get_insider function is failing in util.py with this error:
File "h:\anaconda3\lib\site-packages\finvizfinance\insider.py", line 88, in get_insider
info_dict[table_header[i]] = number_covert(col.text)
File "h:\anaconda3\lib\site-packages\finvizfinance\util.py", line 148, in number_covert
elif num[-1] == "%":
IndexError: string index out of range

Type of change

• Bug fix (non-breaking change which fixes an issue)

What you did

Changes Made:

• Empty String Check (if not num): This ensures that the code doesn't attempt to access num[-1] if num is empty.
• Stripping Whitespace (num = num.strip()): Removes any leading or trailing whitespace in the string, ensuring clean input.
• Replaced .split(",") with .replace(",", ""): This simplifies removing commas from the string, making it more efficient.

How This Fixes the Problem:
The if not num check ensures that the function won't try to access the last character of an empty string, thus avoiding the IndexError.
If num is "%", "B", "M", or "K", the function properly processes the string and converts it to the corresponding float.
If num is just a plain number with commas, it will remove the commas and convert the number to a float.