Properly migrate sources who have no submissions stored
Properly migrate sources who have no submissions stored

chadmiller/securedrop,ehartsuyker/securedrop,pwplus/securedrop,kelcecil/securedrop,jaseg/securedrop,jeann2013/securedrop,pwplus/securedrop,ehartsuyker/securedrop,garrettr/securedrop,GabeIsman/securedrop,jaseg/securedrop,jrosco/securedrop,jrosco/securedrop,jeann2013/securedrop,chadmiller/securedrop,harlo/securedrop,heartsucker/securedrop,jrosco/securedrop,micahflee/securedrop,jeann2013/securedrop,heartsucker/securedrop,GabeIsman/securedrop,harlo/securedrop,kelcecil/securedrop,garrettr/securedrop,jeann2013/securedrop,kelcecil/securedrop,ageis/securedrop,chadmiller/securedrop,ageis/securedrop,heartsucker/securedrop,ageis/securedrop,jeann2013/securedrop,micahflee/securedrop,GabeIsman/securedrop,harlo/securedrop,conorsch/securedrop,harlo/securedrop,garrettr/securedrop,jrosco/securedrop,GabeIsman/securedrop,pwplus/securedrop,micahflee/securedrop,pwplus/securedrop,GabeIsman/securedrop,ehartsuyker/securedrop,jrosco/securedrop,garrettr/securedrop,pwplus/securedrop,jaseg/securedrop,conorsch/securedrop,ehartsuyker/securedrop,GabeIsman/securedrop,kelcecil/securedrop,micahflee/securedrop,heartsucker/securedrop,harlo/securedrop,jaseg/securedrop,ageis/securedrop,harlo/securedrop,jeann2013/securedrop,conorsch/securedrop,conorsch/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,chadmiller/securedrop,kelcecil/securedrop,jrosco/securedrop,jaseg/securedrop,conorsch/securedrop,heartsucker/securedrop,jaseg/securedrop,kelcecil/securedrop,chadmiller/securedrop,pwplus/securedrop,chadmiller/securedrop