Fixes for the /echo command (#4843)

api/command_echo.go

@@ -40,6 +40,10 @@ func (me *EchoProvider) GetCommand(c *Context) *model.Command {
 }
 
 func (me *EchoProvider) DoCommand(c *Context, args *model.CommandArgs, message string) *model.CommandResponse {
+	if len(message) == 0 {
+		return &model.CommandResponse{Text: c.T("api.command_echo.message.app_error"), ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL}
+	}
+
 	maxThreads := 100
 
 	delay := 0

api/command_echo_test.go

@@ -17,8 +17,11 @@ func TestEchoCommand(t *testing.T) {
 
 	echoTestString := "/echo test"
 
-	r1 := Client.Must(Client.Command(channel1.Id, echoTestString)).Data.(*model.CommandResponse)
-	if r1 == nil {
+	if r1 := Client.Must(Client.Command(channel1.Id, echoTestString)).Data.(*model.CommandResponse); r1 == nil {
+		t.Fatal("Echo command failed to execute")
+	}
+
+	if r1 := Client.Must(Client.Command(channel1.Id, "/echo ")).Data.(*model.CommandResponse); r1 == nil {
 		t.Fatal("Echo command failed to execute")
 	}