fixed error handler in Background _sigchld_handler()
fixed error handler in Background _sigchld_handler()

mrakitin/sirepo,radiasoft/sirepo,mkeilman/sirepo,mkeilman/sirepo,mkeilman/sirepo,mrakitin/sirepo,radiasoft/sirepo,mkeilman/sirepo,mrakitin/sirepo,mrakitin/sirepo,radiasoft/sirepo,radiasoft/sirepo,radiasoft/sirepo