chatgui: clear clipboard before setText for reliable copy on Linux

tools/chatgui/src/chatview.cpp

@@ -133,6 +133,7 @@ void ChatView::copySelection() {
         QString text = idx.data(MsgTextRole).toString();
         if (m_textSel.startChar >= 0 && m_textSel.endChar > m_textSel.startChar)
             text = text.mid(m_textSel.startChar, m_textSel.endChar - m_textSel.startChar);
+        QApplication::clipboard()->clear(QClipboard::Clipboard);
         QApplication::clipboard()->setText(text);
     } else {
         QString r;
@@ -145,6 +146,7 @@ void ChatView::copySelection() {
             r += idx.data(MsgAuthorRole).toString() + ": ";
             r += idx.data(MsgTextRole).toString();
         }
+        QApplication::clipboard()->clear(QClipboard::Clipboard);
         QApplication::clipboard()->setText(r);
     }
 }