fix: NPE in tobago-tree

Issue: TOBAGO-1633
diff --git a/tobago-core/src/main/java/org/apache/myfaces/tobago/internal/renderkit/renderer/TreeSelectRenderer.java b/tobago-core/src/main/java/org/apache/myfaces/tobago/internal/renderkit/renderer/TreeSelectRenderer.java
index 69152ec..e903c75 100644
--- a/tobago-core/src/main/java/org/apache/myfaces/tobago/internal/renderkit/renderer/TreeSelectRenderer.java
+++ b/tobago-core/src/main/java/org/apache/myfaces/tobago/internal/renderkit/renderer/TreeSelectRenderer.java
@@ -47,6 +47,7 @@
 import javax.faces.context.FacesContext;
 import java.io.IOException;
 import java.lang.invoke.MethodHandles;
+import java.util.Map;
 
 public class TreeSelectRenderer extends RendererBase {
 
@@ -136,9 +137,14 @@
       writer.endElement(HtmlElements.INPUT);
 
       final CommandMap behaviorCommands = getBehaviorCommands(facesContext, treeSelect);
-      Command change = behaviorCommands.getOther().get(ClientBehaviors.change);
-      change.setExecute(change.getExecute() + " " + tree.getClientId(facesContext));
-      change.setRender(change.getRender() + " " + tree.getClientId(facesContext));
+      if (behaviorCommands != null) {
+        Map<ClientBehaviors, Command> other = behaviorCommands.getOther();
+        if (other != null) {
+          Command change = other.get(ClientBehaviors.change);
+          change.setExecute(change.getExecute() + " " + tree.getClientId(facesContext));
+          change.setRender(change.getRender() + " " + tree.getClientId(facesContext));
+        }
+      }
       encodeBehavior(writer, behaviorCommands);
     }