test(event): reset EventPluginLoader filterQuery before each test

Defensively clear singleton filterQuery in @before to prevent
preceding tests in the same JVM batch (forkEvery=100) from
leaving stale state that causes matchFilter to return false.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: warku123

framework/src/test/java/org/tron/core/event/BlockEventGetTest.java

@@ -90,6 +90,7 @@ public static void init() {
 
   @Before
   public void before() throws IOException {
+    EventPluginLoader.getInstance().setFilterQuery(null);
     Args.getInstance().setNodeListenPort(10000 + port.incrementAndGet());
 
     dbManager = context.getBean(Manager.class);