Binary search that hangs

A colleague reports that this binary search sometimes throws IndexError and sometimes never returns at all. The input nums is sorted ascending and may be empty. Find every bug without running the code.

1def binary_search(nums, target):
2    left = 0
3    right = len(nums)
4 
5    while left <= right:
6        mid = (left + right) // 2
7 
8        if nums[mid] == target:
9            return mid
10 
11        if nums[mid] < target:
12            left = mid
13        else:
14            right = mid
15 
16    return -1

1. Trace the code on nums = [1, 3, 5], target = 7 and on nums = [1, 3], target = 3. What happens in each case?
2. Identify both bugs and state the loop invariant that each one breaks.
3. Write the corrected function.
4. List the edge cases you would test: empty array, single element, target smaller/larger than everything, duplicates.
5. State the time and space complexity of the corrected version.