chatgui: clear clipboard before setText for reliable copy on Linux

tools/chatgui/src/invitedialog.cpp

@@ -27,9 +27,12 @@ InviteDialog::InviteDialog(const QString& link, QWidget* parent)
     auto *copyBtn = new QPushButton("Скопировать", this);
     connect(copyBtn, &QPushButton::clicked, this, [this, linkEdit]() {
         QClipboard* cb = QApplication::clipboard();
+        cb->clear(QClipboard::Clipboard);
         cb->setText(m_link, QClipboard::Clipboard);
-        if (cb->supportsSelection())
+        if (cb->supportsSelection()) {
+            cb->clear(QClipboard::Selection);
             cb->setText(m_link, QClipboard::Selection);
+        }
         linkEdit->setFocus();
     });
     btnLayout->addWidget(copyBtn);