Fix workflow task imports
Fix workflow task imports

Empty Task type field should not cause imports to fail. Lines without
that value must default to the default value specified in the task group
task model.

prasannav7/ggrc-core,j0gurt/ggrc-core,VinnieJohns/ggrc-core,j0gurt/ggrc-core,selahssea/ggrc-core,NejcZupec/ggrc-core,plamut/ggrc-core,jmakov/ggrc-core,selahssea/ggrc-core,AleksNeStu/ggrc-core,AleksNeStu/ggrc-core,kr41/ggrc-core,VinnieJohns/ggrc-core,andrei-karalionak/ggrc-core,VinnieJohns/ggrc-core,NejcZupec/ggrc-core,prasannav7/ggrc-core,VinnieJohns/ggrc-core,NejcZupec/ggrc-core,edofic/ggrc-core,j0gurt/ggrc-core,andrei-karalionak/ggrc-core,josthkko/ggrc-core,jmakov/ggrc-core,j0gurt/ggrc-core,josthkko/ggrc-core,andrei-karalionak/ggrc-core,jmakov/ggrc-core,plamut/ggrc-core,josthkko/ggrc-core,selahssea/ggrc-core,jmakov/ggrc-core,NejcZupec/ggrc-core,edofic/ggrc-core,jmakov/ggrc-core,selahssea/ggrc-core,prasannav7/ggrc-core,edofic/ggrc-core,kr41/ggrc-core,prasannav7/ggrc-core,kr41/ggrc-core,plamut/ggrc-core,kr41/ggrc-core,josthkko/ggrc-core,AleksNeStu/ggrc-core,plamut/ggrc-core,AleksNeStu/ggrc-core,edofic/ggrc-core,andrei-karalionak/ggrc-core