Avoid None being passed to env_to_dictionary
Avoid None being passed to env_to_dictionary


Former-commit-id: 9860195e3ad6aaa3d16c7ca6dfa76aba06ef1f88
plwhite/libcalico,Symmetric/libcalico,caseydavenport/libcalico,TrimBiggs/libnetwork-plugin,djosborne/libcalico,tomdee/libnetwork-plugin,projectcalico/libcalico,tomdee/libcalico,robbrockbank/libcalico,TrimBiggs/libcalico,insequent/libcalico,alexhersh/libcalico,projectcalico/libnetwork-plugin,TrimBiggs/libnetwork-plugin,L-MA/libcalico