SDOE NUSF Bug When Design Size Equals Candidate Set Size

[bpaul4]

To reproduce the issue:

1. In the SDOE toolbox, load the data file with columns (Label, X1, X2, Values). Our file had only 12 points, which is much smaller than surf1candidates from the tutorial.
2. Set the Design Construction to Non-Uniform Space Filling and open the SDOE dialog.
3. Uncheck __id and set Label to Index. Set Values to Weights.
4. (RAN CORRECTLY) Set the Design Size to a number smaller than the number of candidate points, for us design size = 11 ran with no issues.
5. (THROWS ERROR) Set the Design Size to the dataset size (design size = 12 for us), fails on line 406 in nusf.py with "local variable best_mdpts referenced before assignment".