Crash report window does not open on GitHub source builds

When using a source build of 4.12, the crash report client window does not open even if Crash Report Client is manually built alongside the editor.

UPDATE:
Only affecting Source builds from Github. Perforce builds are showing the crash report window as expected.

Regression:
Yes

Working in 4.11.2 - CL 2946394
Broken in 4.12.0 - CL 2992821

1. Open UE4 source engine from GitHub
2. Create new project
3. Open command line and enter "debug crash" command

Result:
White dialog box opens instead of crash report client window (Attached screenshot)

Expected:
Black crash reporter window opens