Fix crash when HTTP_PROXY env contains no auth

[dmach]

Fixes: #1363

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01 ⚠️

Comparison is base (ac23ed0) 28.85% compared to head (eaad34f) 28.85%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1366      +/-   ##
==========================================
- Coverage   28.85%   28.85%   -0.01%     
==========================================
  Files          45       45              
  Lines       17069    17070       +1     
==========================================
  Hits         4925     4925              
- Misses      12144    12145       +1     

Impacted Files	Coverage Δ
osc/_private/project.py	0.00% <0.00%> (ø)
osc/connection.py	53.14% <0.00%> (-0.14%)	⬇️

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