pcie: fixed filpped empty check

It's obvious that we want to skip if the string is empty, not if it is
valid.

Tested: code compiles. Trivial change.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I892e81fb0f87a8999eb880100fd284419054eece
diff --git a/redfish-core/lib/pcie.hpp b/redfish-core/lib/pcie.hpp
index 9bc2dbf..327e79e 100644
--- a/redfish-core/lib/pcie.hpp
+++ b/redfish-core/lib/pcie.hpp
@@ -320,7 +320,7 @@
                         property = std::get_if<std::string>(&propEntry.second);
                     }
                 }
-                if (property == nullptr || !property->empty())
+                if (property == nullptr || property->empty())
                 {
                     continue;
                 }