🐛 Fix: Handle null key in IterativeBinarySearch

Description

The current implementation of IterativeBinarySearch handles null and empty arrays but does not account for a null search key.

This can lead to a NullPointerException when calling:

key.compareTo(array[mid])

Changes Made

• Added a null check for the key parameter in the find method:

if (array == null || array.length == 0 || key == null) {
    return -1;
}

Why this is important

• Prevents runtime crashes when a null key is passed
• Improves robustness and defensive programming
• Ensures consistent behavior across edge cases

Type of change

• Bug fix
• New feature
• Documentation update

Checklist

• I have read the contributing guidelines
• This is my own work
• Code follows project conventions