qt, refactor: Fix 'split is deprecated' warnings

src/qt/guiutil.h

@@ -320,6 +320,27 @@ namespace GUIUtil
     bool HasPixmap(const QLabel* label);
     QImage GetImage(const QLabel* label);
 
+    /**
+     * Splits the string into substrings wherever separator occurs, and returns
+     * the list of those strings. Empty strings do not appear in the result.
+     *
+     * QString::split() signature differs in different Qt versions:
+     *  - QString::SplitBehavior is deprecated since Qt 5.15
+     *  - Qt::SplitBehavior was introduced in Qt 5.14
+     * If {QString|Qt}::SkipEmptyParts behavior is required, use this
+     * function instead of QString::split().
+     */
+    template <typename SeparatorType>
+    QStringList SplitSkipEmptyParts(const QString& string, const SeparatorType& separator)
+    {
+    #if (QT_VERSION >= QT_VERSION_CHECK(5, 14, 0))
+        return string.split(separator, Qt::SkipEmptyParts);
+    #else
+        return string.split(separator, QString::SkipEmptyParts);
+    #endif
+    }
+
+
 } // namespace GUIUtil
 
 #endif // BITCOIN_QT_GUIUTIL_H

src/qt/optionsmodel.cpp

@@ -219,7 +219,7 @@ static ProxySetting GetProxySetting(QSettings &settings, const QString &name)
         return default_val;
     }
     // contains IP at index 0 and port at index 1
-    QStringList ip_port = settings.value(name).toString().split(":", QString::SkipEmptyParts);
+    QStringList ip_port = GUIUtil::SplitSkipEmptyParts(settings.value(name).toString(), ":");
     if (ip_port.size() == 2) {
         return {true, ip_port.at(0), ip_port.at(1)};
     } else { // Invalid: return default

src/qt/transactionview.cpp

@@ -237,7 +237,7 @@ void TransactionView::setModel(WalletModel *_model)
         if (_model->getOptionsModel())
         {
             // Add third party transaction URLs to context menu
-            QStringList listUrls = _model->getOptionsModel()->getThirdPartyTxUrls().split("|", QString::SkipEmptyParts);
+            QStringList listUrls = GUIUtil::SplitSkipEmptyParts(_model->getOptionsModel()->getThirdPartyTxUrls(), "|");
             for (int i = 0; i < listUrls.size(); ++i)
             {
                 QString url = listUrls[i].trimmed();