Send empty http response when body is nil (#80196)

* build empty response if body is nil

* fix test

pkg/api/response/response.go

@@ -311,6 +311,8 @@ func Respond(status int, body any) *NormalResponse {
 		b = t
 	case string:
 		b = []byte(t)
+	case nil:
+		break
 	default:
 		var err error
 		if b, err = json.Marshal(body); err != nil {

pkg/api/response/response_test.go

@@ -125,3 +125,49 @@ func TestErrors(t *testing.T) {
 		)
 	}
 }
+
+func TestRespond(t *testing.T) {
+	testCases := []struct {
+		name     string
+		status   int
+		body     any
+		expected []byte
+	}{
+		{
+			name:     "with body of type []byte",
+			status:   200,
+			body:     []byte("message body"),
+			expected: []byte("message body"),
+		},
+		{
+			name:     "with body of type string",
+			status:   400,
+			body:     "message body",
+			expected: []byte("message body"),
+		},
+		{
+			name:     "with nil body",
+			status:   204,
+			body:     nil,
+			expected: nil,
+		},
+		{
+			name:   "with body of type struct",
+			status: 200,
+			body: struct {
+				Name  string
+				Value int
+			}{"name", 1},
+			expected: []byte(`{"Name":"name","Value":1}`),
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			resp := Respond(tc.status, tc.body)
+
+			require.Equal(t, tc.status, resp.status)
+			require.Equal(t, tc.expected, resp.body.Bytes())
+		})
+	}
+}

pkg/services/publicdashboards/api/api_test.go

@@ -269,10 +269,7 @@ func TestAPIDeletePublicDashboard(t *testing.T) {
 			assert.Equal(t, test.ExpectedHttpResponse, response.Code)
 
 			if test.ExpectedHttpResponse == http.StatusOK {
-				var jsonResp any
+				assert.Equal(t, []byte(nil), response.Body.Bytes())
-				err := json.Unmarshal(response.Body.Bytes(), &jsonResp)
-				require.NoError(t, err)
-				assert.Equal(t, jsonResp, nil)
 			}
 
 			if !test.ShouldCallService {