Bug: merge_sorted drops trailing elements

[windsornguyen]

Description

mathutils.core.merge_sorted drops the remaining elements when one input list is exhausted before the other.

Reproduction

from mathutils.core import merge_sorted

# Expected: [1, 2, 3, 4, 5]
# Actual:   [1, 2, 3, 4]
merge_sorted([1, 3, 5], [2, 4])

Failing tests

FAILED tests/test_core.py::test_merge_sorted_unequal_length
FAILED tests/test_core.py::test_merge_sorted_empty_left
FAILED tests/test_core.py::test_merge_sorted_empty_right

Expected behavior

After the main merge loop, the remaining elements from whichever list isn't exhausted should be appended to the result.

[windsornguyen]

@cind fix