add null check in EntityProxy.equals and remove unused variable in test

Author: bachuv

client/src/main/java/com/microsoft/durabletask/EntityProxy.java

@@ -107,6 +107,9 @@ public Object invoke(Object proxy, Method method, Object[] args) throws Throwabl
                     case "hashCode":
                         return entityId.hashCode();
                     case "equals":
+                        if (args == null || args.length == 0) {
+                            return false;
+                        }
                         if (args[0] == proxy) {
                             return true;
                         }

client/src/test/java/com/microsoft/durabletask/TaskOrchestrationEntityEventTest.java

@@ -763,7 +763,7 @@ void callEntity_nullResultViaEventRaised_triggerBindingPath() throws Exception {
 
         TaskOrchestrationExecutor executor = createExecutor(orchestratorName, ctx -> {
             // Void operation — result is null
-            Void value = ctx.callEntity(entityId, "reset", null, Void.class).await();
+            ctx.callEntity(entityId, "reset", null, Void.class).await();
             ctx.complete("done");
         });