add test case for throw error

Author: Sunny Jiao

framework/src/test/java/org/tron/core/WalletTest.java

@@ -857,6 +857,20 @@ public void testGetDelegatedResourceV2() {
     }
   }
 
+  @Test
+  public void testGetPaginatedNowWitnessList_Error() {
+    try {
+      // To avoid throw MaintenanceClearingException
+      dbManager.getChainBaseManager().getDynamicPropertiesStore().saveStateFlag(1);
+      wallet.getPaginatedNowWitnessList(0, 10);
+      Assert.fail("Should throw error when in maintenance period");
+    } catch (Exception e) {
+      Assert.assertTrue("Should throw MaintenanceClearingException",
+          e instanceof MaintenanceClearingException);
+    }
+    dbManager.getChainBaseManager().getDynamicPropertiesStore().saveStateFlag(0);
+  }
+
   @Test
   public void testGetPaginatedNowWitnessList_CornerCase() {
     try {