XWIKI-23523: Livedata crash with NPE when used with custom data source (#4571)

Author: Josue-T

xwiki-platform-core/xwiki-platform-livedata/xwiki-platform-livedata-api/src/main/java/org/xwiki/livedata/internal/DefaultLiveDataConfigurationResolver.java

@@ -116,7 +116,11 @@ private LiveDataConfiguration mergeBaseConfig(LiveDataConfiguration config) thro
         // Prevent null values (make the configuration explicit).
         mergedConfig.initialize();
 
-        handleLayouts(config.getMeta().getLayouts(), mergedConfig.getMeta());
+        Collection<LiveDataLayoutDescriptor> layout = null;
+        if (config.getMeta() != null) {
+            layout = config.getMeta().getLayouts();
+        }
+        handleLayouts(layout, mergedConfig.getMeta());
         handlePageSizes(mergedConfig);
 
         // Translate using the context locale.

xwiki-platform-core/xwiki-platform-livedata/xwiki-platform-livedata-api/src/test/java/org/xwiki/livedata/internal/DefaultLiveDataConfigurationResolverTest.java

@@ -176,6 +176,22 @@ void withInitialize() throws Exception
             this.resolver.resolve(this.resolver.resolve(config)));
     }
 
+    /**
+     * Test to avoid regression on XWIKI-23523.
+     * We need to ensure that we can resolve a configuration with meta=null.
+     */
+    @Test
+    void withMetaNull() throws Exception
+    {
+        LiveDataConfiguration config = new LiveDataConfiguration();
+        config.initialize();
+        config.setMeta(null);
+        String expected = FileUtils.readFileToString(new File("src/test/resources/withInitialize.json"),
+            Charset.defaultCharset());
+        assertEquals(this.objectMapper.readValue(expected, LiveDataConfiguration.class),
+            this.resolver.resolve(this.resolver.resolve(config)));
+    }
+
     private static Stream<String[]> getTestData() throws Exception
     {
         return DATA_PROVIDER.getTestData(new File("src/test/resources/DefaultLiveDataConfigurationResolver.test"));