FENNEL (dt): more robust CalcXO.   When the Calculator fails to compute an output row, the XO skips the row but continues running.
FENNEL (dt): more robust CalcXO. 
 When the Calculator fails to compute an output row, the XO skips the row but continues running.

[git-p4: depot-paths = "//open/dt/dev/": change = 6082]

LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb,LucidDB/luciddb