[LyX/master] Do not set layout for no-op paragraph break

[Jean-Marc Lasgouttes]

commit 2ad52918da1d0f375bf2831df4c51f6afa7ea448
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Wed Aug 24 15:29:17 2016 +0200

    Do not set layout for no-op paragraph break
    
    When breaking paragraph in an empty top-level paragraph, nothing
    happens on screen but yet there is an undo step because the layout is
    reset to what it already was.
    
    Avoid this case.
    
    Fixes bug #10089.
---
 src/Text.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/Text.cpp b/src/Text.cpp
index 00b575b..007271d 100644
--- a/src/Text.cpp
+++ b/src/Text.cpp
@@ -743,7 +743,8 @@ void Text::breakParagraph(Cursor & cur, bool inverse_logic)
                else {
                        docstring const & lay = cur.paragraph().usePlainLayout()
                            ? tclass.plainLayoutName() : 
tclass.defaultLayoutName();
-                       setLayout(cur, lay);
+                       if (lay != layout.name())
+                               setLayout(cur, lay);
                }
                return;
        }