s_format: replace an assertion by a warning
s_format: replace an assertion by a warning

chubbymaggie/angr,chubbymaggie/simuvex,axt/angr,tyb0807/angr,schieb/angr,angr/simuvex,chubbymaggie/angr,chubbymaggie/simuvex,iamahuman/angr,axt/angr,chubbymaggie/angr,schieb/angr,f-prettyland/angr,tyb0807/angr,angr/angr,iamahuman/angr,axt/angr,angr/angr,iamahuman/angr,tyb0807/angr,f-prettyland/angr,schieb/angr,f-prettyland/angr,chubbymaggie/simuvex,angr/angr