LibGUI: Clear inactive selections in DisplayOnly TextEditors

Author: https://github.com/thankyouverycool
Commit: bc26d1093f
Pull-request: https://github.com/SerenityOS/serenity/pull/5741
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/emanuele6

Userland/Libraries/LibGUI/TextEditor.cpp

@@ -1133,6 +1133,8 @@ void TextEditor::focusin_event(FocusEvent& event)
 
 void TextEditor::focusout_event(FocusEvent&)
 {
+    if (is_displayonly() && has_selection())
+        m_selection.clear();
     stop_timer();
     if (on_focusout)
         on_focusout();