refactor: some Application & style things (#5561)

src/util/FormatTime.cpp

@@ -48,7 +48,7 @@ QString formatTime(int totalSeconds)
     return res;
 }
 
-QString formatTime(QString totalSecondsString)
+QString formatTime(const QString &totalSecondsString)
 {
     bool ok = true;
     int totalSeconds(totalSecondsString.toInt(&ok));

src/util/FormatTime.hpp

@@ -8,7 +8,7 @@ namespace chatterino {
 
 // format: 1h 23m 42s
 QString formatTime(int totalSeconds);
-QString formatTime(QString totalSecondsString);
+QString formatTime(const QString &totalSecondsString);
 QString formatTime(std::chrono::seconds totalSeconds);
 
 }  // namespace chatterino

src/util/PostToThread.hpp

@@ -10,7 +10,7 @@ namespace chatterino {
 // https://stackoverflow.com/questions/21646467/how-to-execute-a-functor-or-a-lambda-in-a-given-thread-in-qt-gcd-style
 // Qt 5/4 - preferred, has least allocations
 template <typename F>
-static void postToThread(F &&fun, QObject *obj = qApp)
+static void postToThread(F &&fun, QObject *obj = QCoreApplication::instance())
 {
     struct Event : public QEvent {
         using Fun = typename std::decay<F>::type;