fix: throw an error when trying to edit config for nonexistent app

cli/app/config.go

@@ -37,6 +37,9 @@ var appConfigCommand = &cli.Command{
 			logrus.Fatal(err)
 		}
 
+		if appFiles[appName].Path == "" {
+			return errors.New("app doesn't exist")
+		}
 		cmd := exec.Command(ed, appFiles[appName].Path)
 		cmd.Stdin = os.Stdin
 		cmd.Stdout = os.Stdout