If there is only 1 study for each grouping parameter, the Test for Outlying Slopes is not performed and there is no output document for Test for Outlying Slopes, Test for Outlying Slopes ANOVA table, Test for outlying slopes coefficients. This prevents the Identify Alarms node to be run and emails are not sent. Although there technically can't be an outlying slope if there is only 1 study for the grouping parameter, there still needs to be a blank output so the workspace can continue.