Fix build with Qt 5.5.

src/app/cli/jsoncliformatter.cpp

@@ -184,8 +184,13 @@ void JsonCliFormatter::writeError(CliError errorCode)
 {
   QString msg;
   if (errorCode == CliError::MethodNotFound) {
+#if QT_VERSION >= 0x050600
     msg = tr("Unknown command '%1'")
         .arg(m_args.isEmpty() ? QLatin1String("") : m_args.constFirst());
+#else
+    msg = tr("Unknown command '%1'")
+        .arg(m_args.isEmpty() ? QLatin1String("") : m_args.first());
+#endif
   }
   writeErrorMessage(msg, jsonRpcErrorCode(errorCode));
 }

src/app/cli/kid3cli.cpp

@@ -180,7 +180,11 @@ Kid3Cli::Kid3Cli(Kid3Application* app,
 {
   m_formatters << new JsonCliFormatter(io)
                << new TextCliFormatter(io);
+#if QT_VERSION >= 0x050600
   m_formatter = m_formatters.constLast();
+#else
+  m_formatter = m_formatters.last();
+#endif
 
   m_cmds << new HelpCommand(this)
          << new TimeoutCommand(this)
@@ -244,7 +248,11 @@ CliCommand* Kid3Cli::commandForArgs(const QString& line)
     return nullptr;
 
   // Default to the last formatter
+#if QT_VERSION >= 0x050600
   m_formatter = m_formatters.constLast();
+#else
+  m_formatter = m_formatters.last();
+#endif
 
   QStringList args;
   for (auto fmt : m_formatters) {

src/app/cli/textcliformatter.cpp

@@ -177,8 +177,13 @@ void TextCliFormatter::writeError(CliError errorCode)
   QString errorMsg;
   switch (errorCode) {
   case CliError::MethodNotFound:
+#if QT_VERSION >= 0x050600
     errorMsg = tr("Unknown command '%1'. Type 'help' for help.")
         .arg(m_args.isEmpty() ? QLatin1String("") : m_args.constFirst());
+#else
+    errorMsg = tr("Unknown command '%1'. Type 'help' for help.")
+        .arg(m_args.isEmpty() ? QLatin1String("") : m_args.first());
+#endif
     break;
   default:
     ;