Fix LocaleContext issues on dialogs on root context

 - info.magnolia.ui.dialog.actions.OpenDialogAction initializes the localeContext based on the valueContext. When it is not set (was not set on root context), the localeContext was not being set, which is required for some fields (e.g. multi value)

src/main/java/com/namics/oss/magnolia/appbuilder/action/add/OpenCreateDialogAction.java

@@ -3,7 +3,9 @@
 import info.magnolia.i18nsystem.I18nizer;
 import info.magnolia.ui.UIComponent;
 import info.magnolia.ui.ValueContext;
+import info.magnolia.ui.api.action.ActionExecutionException;
 import info.magnolia.ui.api.i18n.I18NAuthoringSupport;
+import info.magnolia.ui.datasource.jcr.JcrDatasource;
 import info.magnolia.ui.dialog.DialogDefinition;
 import info.magnolia.ui.dialog.DialogDefinitionRegistry;
 import info.magnolia.ui.dialog.actions.OpenDialogAction;
@@ -13,17 +15,23 @@
 
 public class OpenCreateDialogAction extends OpenDialogAction<Node> {
 	private final OpenCreateDialogActionDefinition definition;
+	private final JcrDatasource jcrDatasource;
+	private final ValueContext<Node> valueContext;
 
 	public OpenCreateDialogAction(
 			final OpenCreateDialogActionDefinition definition,
 			final LocaleContext localeContext,
+			final JcrDatasource jcrDatasource,
 			final ValueContext<Node> valueContext,
 			final UIComponent parentView,
 			final I18NAuthoringSupport<Node> i18NAuthoringSupport,
 			final DialogDefinitionRegistry dialogDefinitionRegistry,
-			final I18nizer i18nizer) {
+			final I18nizer i18nizer
+	) {
 		super(definition, localeContext, valueContext, parentView, i18NAuthoringSupport, dialogDefinitionRegistry, i18nizer);
 		this.definition = definition;
+		this.jcrDatasource = jcrDatasource;
+		this.valueContext = valueContext;
 	}
 
 	@Override
@@ -32,4 +40,16 @@ protected DialogDefinition getDialogDefinition(final DialogDefinitionRegistry di
 		dialogDefinition.getActions().put("commit", definition.getCommitAction()); //we can't generate a new map due to byteBuddy (I18nizer), but since it is a mutable hash map this is fine
 		return i18nizer.decorate(dialogDefinition);
 	}
+
+	@Override
+	public void execute() throws ActionExecutionException {
+		try {
+			if (valueContext.getSingle().isEmpty()) {
+				valueContext.set(jcrDatasource.getRoot());
+			}
+			super.execute();
+		} catch (Exception e) {
+			throw new ActionExecutionException(e);
+		}
+	}
 }