[LyX/2.1.x] Make the fix for bug 8999 actually work

[Georg Baum]

commit 8b31f838c5ceab2cc9aae03e31cdcc673c2a4381
Author: Georg Baum <b...@lyx.org>
Date:   Fri Nov 14 21:28:40 2014 +0100

    Make the fix for bug 8999 actually work
    
    This backports 1cdbb94f which was spotted by cppcheck.

diff --git a/src/mathed/MathMacro.cpp b/src/mathed/MathMacro.cpp
index f39112c..4483412 100644
--- a/src/mathed/MathMacro.cpp
+++ b/src/mathed/MathMacro.cpp
@@ -329,10 +329,11 @@ private:
 void MathMacro::updateRepresentation(Cursor * cur, MacroContext const & mc,
                UpdateType utype)
 {
+       // block recursive calls (bug 8999)
        if (isUpdating_)
                return;
 
-       UpdateLocker(*this);
+       UpdateLocker locker(*this);
 
        // known macro?
        if (macro_ == 0)