You can convert the Lookup formula to return 0 when B2107 is blank

=IF(B2107="",0,(LOOKUP(B2107,$BB$6:$BB$17,$BC$6:$BC$17))*V2107)

or

you can change formula in Sheet B to something like:

=if(ISNA(SheetB!B2107),0,SheetB!B2107)