webapp/billing: being more defensive against "missing data" from stripe
webapp/billing: being more defensive against "missing data" from stripe

tscholl2/smc,DrXyzzy/smc,DrXyzzy/smc,sagemathinc/smc,sagemathinc/smc,sagemathinc/smc,DrXyzzy/smc,DrXyzzy/smc,tscholl2/smc,tscholl2/smc,tscholl2/smc,sagemathinc/smc,tscholl2/smc