fix: handle empty auth models list in readlatest auth model (#265)

Author: SoulPancake

src/main/java/dev/openfga/sdk/api/client/model/ClientReadAuthorizationModelResponse.java

@@ -34,7 +34,10 @@ public static ClientReadAuthorizationModelResponse latestOf(
         ClientReadAuthorizationModelResponse clientResponse = new ClientReadAuthorizationModelResponse(
                 apiResponse.getStatusCode(), apiResponse.getHeaders(), apiResponse.getRawResponse());
         ReadAuthorizationModelsResponse response = apiResponse.getData();
-        clientResponse.setAuthorizationModel(response.getAuthorizationModels().get(0));
+        List<dev.openfga.sdk.api.model.AuthorizationModel> models = response.getAuthorizationModels();
+        if (!models.isEmpty()) {
+            clientResponse.setAuthorizationModel(models.get(0));
+        }
         return clientResponse;
     }
 

src/test/java/dev/openfga/sdk/api/client/OpenFgaClientTest.java

@@ -746,6 +746,23 @@ public void readLatestAuthorizationModelTest() throws Exception {
         assertEquals(DEFAULT_SCHEMA_VERSION, authModel.getSchemaVersion());
     }
 
+    @Test
+    public void readLatestAuthorizationModelTest_emptyList() throws Exception {
+        // Given
+        String getUrl = String.format(
+                "%s/stores/%s/authorization-models?page_size=1", FgaConstants.TEST_API_URL, DEFAULT_STORE_ID);
+        String responseBody = "{\"authorization_models\":[]}";
+        mockHttpClient.onGet(getUrl).doReturn(200, responseBody);
+
+        // When
+        ClientReadAuthorizationModelResponse response =
+                fga.readLatestAuthorizationModel().get();
+
+        // Then
+        mockHttpClient.verify().get(getUrl).called(1);
+        assertNull(response.getAuthorizationModel());
+    }
+
     @Test
     public void readChanges() throws Exception {
         // Given