[LyX/master] Additional check for clipboards find buffer support - otherwise Qt complains with unsupported clipboard mode

[Stephan Witt]

commit d65e7a8c87a20b67046ac5cfeaf6961d908b5aeb
Author: Stephan Witt <switt at lyx.org>
Date:   Sun Feb 14 22:18:07 2021 +0100

    Additional check for clipboards find buffer support - otherwise Qt complains with unsupported clipboard mode
---
 src/frontends/qt/GuiClipboard.cpp |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/src/frontends/qt/GuiClipboard.cpp b/src/frontends/qt/GuiClipboard.cpp
index 697977d..6c1d981 100644
--- a/src/frontends/qt/GuiClipboard.cpp
+++ b/src/frontends/qt/GuiClipboard.cpp
@@ -554,7 +554,9 @@ void GuiClipboard::setFindBuffer(docstring const & text)
 {
 	LYXERR(Debug::CLIPBOARD, "new findbuffer: " << text);
 	Clipboard::setFindBuffer(text);
-	qApp->clipboard()->setText(toqstr(text), QClipboard::FindBuffer);
+	if(qApp->clipboard()->supportsFindBuffer()) {
+		qApp->clipboard()->setText(toqstr(text), QClipboard::FindBuffer);
+	}
 }