[LyX/master] Revert "Revert "Only set dummy X11 selection if we do not own it""

[Scott Kostyshak]

commit 5d96ee69eb9173779932575cb6d6ce70db9860b9
Author: Scott Kostyshak <skostysh at lyx.org>
Date:   Tue May 4 12:33:30 2021 -0400

    Revert "Revert "Only set dummy X11 selection if we do not own it""
    
    This reverts commit 1b704b6267bb8144a410c02595887b0731cf4d53.
    
    (the initial reversion was done unintentionally)
---
 src/frontends/qt/GuiSelection.cpp |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/frontends/qt/GuiSelection.cpp b/src/frontends/qt/GuiSelection.cpp
index 0eb3d51..e10bb47 100644
--- a/src/frontends/qt/GuiSelection.cpp
+++ b/src/frontends/qt/GuiSelection.cpp
@@ -51,9 +51,10 @@ void GuiSelection::haveSelection(bool own)
 	// an application actually requests it.
 	// This way calling Selection::have() is cheap and we can do it as
 	// often as we want.
-	//LYXERR(Debug::SELECTION, "GuiSelection: setting dummy selection");
-	if (own)
+	if (own && !qApp->clipboard()->ownsSelection()) {
+		LYXERR(Debug::SELECTION, "GuiSelection: setting dummy selection");
 		qApp->clipboard()->setText(QString(), QClipboard::Selection);
+	}
 	// We don't need to do anything if own = false, as this case is
 	// handled by QT.
 	// FIXME (gb): This is wrong. What is missing here is rather a call of