Fix joining a path when the existing path is empty

[bdraco]

What do these changes do?

The change in #1116 did not cover the case where the current path was "" and other path joined. Fix for a regression introduced in #1082

Are there changes in behavior for the user?

bugfix

Related issue number

fixes #1116

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.12%. Comparing base (c3e4197) to head (5a32096).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1118   +/-   ##
=======================================
  Coverage   95.12%   95.12%           
=======================================
  Files          30       30           
  Lines        4633     4640    +7     
  Branches      410      411    +1     
=======================================
+ Hits         4407     4414    +7     
  Misses        200      200           
  Partials       26       26           

Flag	Coverage Δ
CI-GHA	95.08% <100.00%> (+<0.01%)	⬆️
MyPy	41.11% <37.50%> (-0.03%)	⬇️
OS-Linux	99.38% <100.00%> (+<0.01%)	⬆️
OS-Windows	99.47% <100.00%> (+<0.01%)	⬆️
OS-macOS	99.08% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	98.97% <100.00%> (+<0.01%)	⬆️
Py-3.10.14	99.21% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	99.21% <100.00%> (+<0.01%)	⬆️
Py-3.12.5	99.21% <100.00%> (+<0.01%)	⬆️
Py-3.13.0-rc.1	99.21% <100.00%> (+<0.01%)	⬆️
Py-3.8.10	98.92% <100.00%> (+<0.01%)	⬆️
Py-3.8.18	99.16% <100.00%> (+<0.01%)	⬆️
Py-3.9.13	98.92% <100.00%> (+<0.01%)	⬆️
Py-3.9.19	99.16% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.11	99.22% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	99.21% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.17	99.24% <100.00%> (+<0.01%)	⬆️
VM-macos-latest	99.08% <100.00%> (+<0.01%)	⬆️
VM-ubuntu-latest	99.38% <100.00%> (+<0.01%)	⬆️
VM-windows-latest	99.47% <100.00%> (+<0.01%)	⬆️
pytest	99.38% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.