[LyX/master] Fix bug #11850.

[Richard Kimberly Heck]

commit b5a5a529a38c6e4e09f6e089e4725d5b77993efc
Author: Richard Kimberly Heck <rikiheck at lyx.org>
Date:   Sat Apr 25 01:05:15 2020 -0400

    Fix bug #11850.
    
    When we copy the paragraphs, the Buffer members for the insets are
    not set. As a result, we crash when attempting to access them.
---
 src/Text.cpp |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/src/Text.cpp b/src/Text.cpp
index 1820f05..fa4e2a8 100644
--- a/src/Text.cpp
+++ b/src/Text.cpp
@@ -1801,8 +1801,11 @@ bool Text::dissolveInset(Cursor & cur)
 	pos_type spos = cur.pos();
 	pit_type spit = cur.pit();
 	ParagraphList plist;
-	if (cur.lastpit() != 0 || cur.lastpos() != 0)
+	if (cur.lastpit() != 0 || cur.lastpos() != 0) {
 		plist = paragraphs();
+		for (auto & p : plist)
+			p.setInsetBuffers(*cur.buffer());
+	}
 	cur.popBackward();
 	// update cursor offset
 	if (spit == 0)