test: Return from validateReply if no reply

Return early if actualReply doesn't have value instead of getting the
data even after has_value() failed.

Change-Id: I339324d76a704f8b7bce98cfdf881225e46c5aca
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/test/helper.cpp b/test/helper.cpp
index bbb0410..8587549 100644
--- a/test/helper.cpp
+++ b/test/helper.cpp
@@ -21,6 +21,8 @@
 
     auto actualReply = std::get<1>(reply);
     EXPECT_TRUE(actualReply.has_value());
+    if (!actualReply.has_value())
+        return std::vector<uint8_t>{};
 
     auto data = std::get<0>(*actualReply);
     EXPECT_EQ(hasData, !data.empty());