unit_tests: initialize enough to silence valgrind

tests/unit_tests/serialization.cpp

@@ -394,6 +394,8 @@ TEST(Serialization, serializes_transacion_signatures_correctly)
 
   // Not enough signature vectors for all inputs
   txin_to_key txin_to_key1;
+  txin_to_key1.amount = 1000000000000;
+  memset(txin_to_key1.k_image.data,0,32);
   txin_to_key1.key_offsets.resize(2);
   tx.vin.clear();
   tx.vin.push_back(txin_to_key1);