[LyX/2.3.x] Fix crash when selecting text with changes

[Scott Kostyshak]

commit 0af6a43b6aec8ccc4afe36545a76cd6be727c7b6
Author: Scott Kostyshak <skost...@lyx.org>
Date:   Fri Jul 27 15:28:22 2018 -0400

    Fix crash when selecting text with changes
    
    When selecting text, in some cases a DocIterator could be forwarded
    to a (non-existant) paragraph after the end. The critical part of
    this fix is to break the loop at the correct place. The following
    are additional improvements:
    
    - increase readability by defining a bool named "in_last_par"
    - use cur.selectionEnd().pit() instead of 
cur.selectionEnd().paragraph().id()
    - use it.lastpos() instead of it.paragraph().size()
    
    This commit fixes a regression introduced by 23de5e5e, and reported
    at #11204.
    
    Thanks to Jürgen and JMarc.
    
    (cherry picked from commit d12798759aeb7bae77bec63098fd81f8cc9e554b)
---
 src/Text3.cpp |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/Text3.cpp b/src/Text3.cpp
index e75fad0..b5f9e33 100644
--- a/src/Text3.cpp
+++ b/src/Text3.cpp
@@ -3207,17 +3207,20 @@ bool Text::getStatus(Cursor & cur, FuncRequest const & 
cmd,
                        if (!cur.buffer()->areChangesPresent())
                                break;
 
-                       for (DocIterator it = cur.selectionBegin(); it < 
cur.selectionEnd(); it.forwardPar()) {
+                       for (DocIterator it = cur.selectionBegin(); ; 
it.forwardPar()) {
                                pos_type const beg = it.pos();
                                pos_type end;
-                               if (it.paragraph().id() == 
cur.selectionEnd().paragraph().id())
+                               bool const in_last_par = (it.pit() == 
cur.selectionEnd().pit());
+                               if (in_last_par)
                                        end = cur.selectionEnd().pos();
                                else
-                                       end = it.paragraph().size();
+                                       end = it.lastpos();
                                if (beg != end && it.paragraph().isChanged(beg, 
end)) {
                                        enable = true;
                                        break;
                                }
+                               if (in_last_par)
+                                       break;
                        }
                }
                break;