BUG: CreateDefaultLookupTable crashes if Input is NULL.

TestSetGet.tcl segfaulted when calling GetLookupTable().
GetLookupTable() calls CreateDefaultLookupTable() which requires a
non NULL Input.

Change-Id: I615ec5b386d75d5b64f636156d0006ed15e093a0
Merge topic 'Segfault_PlotBox' into master

b3470426 BUG: CreateDefaultLookupTable crashes if Input is NULL.