Gh 13908 fix bot missing username error (#17854)

Automatic Merge

app/bot.go

@@ -18,6 +18,11 @@ import (
 
 // CreateBot creates the given bot and corresponding user.
 func (a *App) CreateBot(c *request.Context, bot *model.Bot) (*model.Bot, *model.AppError) {
+	vErr := bot.IsValidCreate()
+	if vErr != nil {
+		return nil, vErr
+	}
+
 	user, nErr := a.Srv().Store.User().Save(model.UserFromBot(bot))
 	if nErr != nil {
 		var appErr *model.AppError