Clinic: fix update_graph for functions containing only 1 block
Clinic: fix update_graph for functions containing only 1 block

tyb0807/angr,angr/angr,schieb/angr,angr/angr,tyb0807/angr,schieb/angr,iamahuman/angr,iamahuman/angr,angr/angr,iamahuman/angr,tyb0807/angr,schieb/angr