Fix two compiler warnings (clang 11.0.0)

Found during testing of !122 using clang 11.

Checked by builds on clang 11.0.0, clang 7.0.1-8 (debian10) and gcc 8.3.0
that these fixes cause no regression in build or unit tests
(ninja -v check)

src/primitives/transaction.h

@@ -346,12 +346,7 @@ static inline CTransactionRef MakeTransactionRef(Tx &&txIn) {
 struct PrecomputedTransactionData {
     uint256 hashPrevouts, hashSequence, hashOutputs;
 
-    PrecomputedTransactionData()
-        : hashPrevouts(), hashSequence(), hashOutputs() {}
-
-    PrecomputedTransactionData(const PrecomputedTransactionData &txdata)
-        : hashPrevouts(txdata.hashPrevouts), hashSequence(txdata.hashSequence),
-          hashOutputs(txdata.hashOutputs) {}
+    PrecomputedTransactionData() = default;
 
     template <class T> explicit PrecomputedTransactionData(const T &tx);
 };

src/qt/guiutil.cpp

@@ -915,8 +915,8 @@ QString formatServicesStr(quint64 mask) {
 }
 
 QString formatPingTime(double dPingTime) {
-    return (dPingTime == std::numeric_limits<int64_t>::max() / 1e6 ||
-            dPingTime == 0)
+    return (dPingTime >= double(std::numeric_limits<int64_t>::max()) / 1e6 ||
+            dPingTime <= 0.)
                ? QObject::tr("N/A")
                : QString(QObject::tr("%1 ms"))
                      .arg(QString::number((int)(dPingTime * 1000), 10));