BlockUntilThreadAvailable接口用例添加

https://gitee.com/openharmony/communication_ipc/issues/I7S741Signed-off-by: Ndengyutao <dengyutao2@huawei.com>

ipc/native/test/unittest/common/ipc_skeleton_unittest.cpp

@@ -496,6 +496,9 @@ HWTEST_F(IPCSkeletonTest, SetCallingIdentityTest002, TestSize.Level1)
 HWTEST_F(IPCDfxTest, BlockUntilThreadAvailableTest001, TestSize.Level1)
 {
     IPCDfx *ipcDfxTest = new IPCDfx();
+    if (ipcDfxTest == nullptr) {
+        return;
+    }
     IPCProcessSkeleton *current = IPCProcessSkeleton::GetCurrent();
     if (current != nullptr) {
         ipcDfxTest->BlockUntilThreadAvailable();