Fix handling of invalid best coverage type command line options

[tpn]

E.g. --BestCoverageType=MaximumGraphTraversalDepth instead of --BestCoverageType=HighestMaxGraphTraversalDepth:

C:\perfecthash\src\x64\release\PerfectHashBulkCreate.exe C:\perfecthash-keys\sys32 Chm01 Crc32RotateWXYZ And 11 --AttemptsBeforeTableResize=1000 --MaxNumberOfTableResizes=0 --IgnorePreviousTableSize --FindBestGraph --BestCoverageType=MaximumGraphTraversalDepth --BestCoverageAttempts=10000
c:\perfecthash\src\perfecthash\extractarg.c: 804: TryExtractArgTableCreateParameters failed with error: 3758359093 (0xe0040235).  Unreachable code reached.