I can confirm this by running:
$ /Volumes/Slicer-4.9.0-2018-02-21-macosx-amd64/Slicer.app/Contents/MacOS/Slicer --disable-settings
A workaround is to hit the enter key to bypass the hidden dialog.
Here is the error log -
Session start time .......: 2018-02-22 20:44:34
Slicer version ...........: 4.9.0-2018-02-21 (revision 26937) macosx-amd64 - installed
Operating system .........: Mac OS X / 10.13.3 / 17D47 - 64-bit
Memory ...................: 65536 MB physical, 0 MB virtual
CPU ......................: GenuineIntel Intel(R) Xeon(R) CPU E5-2697 v2 @ 2.70GHz, 12 cores, 24 logical processors
Developer mode enabled ...: no
Prefer executable CLI ....: yes
Additional module paths ..: (none)
Number of registered modules: 136
Popen(%s, cwd=%s, universal_newlines=%s, shell=%s)
Popen(%s, cwd=%s, universal_newlines=%s, shell=%s)
libpng warning: iCCP: known incorrect sRGB profile
Number of instantiated modules: 136
Scripted subject hierarchy plugin registered: Annotations
[6570:80131:0222/204438.066624:ERROR:gl_context_cgl.cc(137)] Error creating context.
[6570:80131:0222/204438.134244:ERROR:gl_context_cgl.cc(137)] Error creating context.
Scripted subject hierarchy plugin registered: SegmentEditor
Scripted subject hierarchy plugin registered: SegmentStatistics
Number of loaded modules: 136
Switch to module: "Welcome"
Uncaught TypeError: channel.execCallbacks[message.id] is not a function