Improve compile times a tiny bit

src/dialogs/ReadReceipts.cpp

@@ -1,5 +1,6 @@
 #include <QDebug>
 #include <QIcon>
+#include <QLabel>
 #include <QListWidgetItem>
 #include <QPainter>
 #include <QPushButton>
@@ -163,3 +164,10 @@ ReadReceipts::paintEvent(QPaintEvent *)
         QPainter p(this);
         style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
+
+void
+ReadReceipts::hideEvent(QHideEvent *event)
+{
+        userList_->clear();
+        QFrame::hideEvent(event);
+}