[LyX/master] Prevent NULL pointer

[Juergen Spitzmueller]

commit c6ef96ea36b0e34c9b61784dc3b7039bf79e5d7b
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Mon Jan 13 13:03:52 2020 +0100

    Prevent NULL pointer
---
 src/Buffer.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index eabb218..c0abc95 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -5348,7 +5348,8 @@ void Buffer::updateBuffer(ParIterator & parit, UpdateType utype) const
 	}
 
 	// set change indicator for the inset
-	parit.inset().asInsetText()->isChanged(changed);
+	if (parit.inset().asInsetText())
+		parit.inset().asInsetText()->isChanged(changed);
 }