Remove assertion that is not necessary.

It may happen that there are errors when doing undo, crashing does not
help in this case.

Fixes bug #12163.

(cherry picked from commit 3e3ad2937c)

src/Undo.cpp

@@ -464,7 +464,6 @@ void Undo::Private::doTextUndoOrRedo(CursorData & cur, UndoElementStack & stack,
 		ErrorList el;
 		cap::switchBetweenClasses(olddc, buffer_.params().documentClassPtr(),
 			static_cast<InsetText &>(buffer_.inset()), el);
-		LATTEST(el.empty());
 	} else if (dit.inMathed()) {
 		// We stored the full cell here as there is not much to be
 		// gained by storing just 'a few' paragraphs (most if not

status.23x

@@ -92,6 +92,8 @@ What's new
 
 - Fix coloring of text-mode material in math equations (bug 11007).
 
+- Fix crash with undo when the document has errors (bug 12163).
+
 
 * INTERNALS