[LyX/master] Fix embarassing crash caused by debug message

[Jean-Marc Lasgouttes]

commit b5d6caac4149cc72cd5a734ffc8e9da1382bc9ee
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Mon Apr 13 12:02:26 2020 +0200

    Fix embarassing crash caused by debug message
    
    After commit 6a936d63, the helpful debug message tries to display
    non-existing elements and crashes the program :(
    
    Fix by radical simplification of the message.
    
    Part of bug #11777.
---
 src/DocIterator.cpp |    6 +-----
 1 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/src/DocIterator.cpp b/src/DocIterator.cpp
index bdad90f..0f4bc10 100644
--- a/src/DocIterator.cpp
+++ b/src/DocIterator.cpp
@@ -633,11 +633,7 @@ void DocIterator::sanitize()
 	for (size_t i = 0, n = sl.size(); i != n; ++i) {
 		if (inset == nullptr) {
 			// FIXME
-			LYXERR0(" Should not happen, but does e.g. after "
-				"C-n C-l C-z S-C-z\n"
-				<< " or when a Buffer has been concurrently edited by two views"
-				<< '\n' << "dit: " << *this << '\n'
-				<< " lastpos: " << slices_[i].lastpos());
+			LYXERR0("Null inset on cursor stack.");
 			fixIfBroken();
 			break;
 		}