Fix errors when widget has no data on input.
Fix errors when widget has no data on input.

kwikadi/orange3,marinkaz/orange3,qPCR4vir/orange3,marinkaz/orange3,marinkaz/orange3,cheral/orange3,cheral/orange3,kwikadi/orange3,qPCR4vir/orange3,qPCR4vir/orange3,qPCR4vir/orange3,qPCR4vir/orange3,kwikadi/orange3,marinkaz/orange3,kwikadi/orange3,kwikadi/orange3,marinkaz/orange3,cheral/orange3,cheral/orange3,qPCR4vir/orange3,cheral/orange3,cheral/orange3,kwikadi/orange3,marinkaz/orange3