editor_archive: fix major bug that prevented certain (many, all?) zip files from being extractable
editor_archive: fix major bug that prevented certain (many, all?) zip files from being extractable

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