[LyX/master] Disable InsetMathKern with invalid lengths (#10539)

[Guillaume Munch]

commit 527cc8ca9c829cbe227667c5c2a57ebce2199606
Author: Guillaume Munch <g...@lyx.org>
Date:   Sun Feb 5 11:04:41 2017 +0100

    Disable InsetMathKern with invalid lengths (#10539)
    
    From now on \kern and \mkern remain as ERT as long as the length is invalid.
    
    Fixes #10539 (regression at 10c8d51b).
    
    The only way to produce an InsetMathKern now is via parsing (i.e. file 
opening
    or copy-paste). This is because there has never been any sensible way to 
input a
    valid InsetMathKern, but this is another issue.
---
 src/mathed/MathFactory.cpp |    2 --
 src/mathed/MathParser.cpp  |    2 +-
 2 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/src/mathed/MathFactory.cpp b/src/mathed/MathFactory.cpp
index 12817a3..3198f80 100644
--- a/src/mathed/MathFactory.cpp
+++ b/src/mathed/MathFactory.cpp
@@ -497,8 +497,6 @@ MathAtom createInsetMath(docstring const & s, Buffer * buf)
                return MathAtom(new InsetMathMakebox(buf, true));
        if (s == "makebox")
                return MathAtom(new InsetMathMakebox(buf, false));
-       if (s == "kern" || s == "mkern")
-               return MathAtom(new InsetMathKern);
        if (s.substr(0, 8) == "xymatrix") {
                char spacing_code = '\0';
                Length spacing;
diff --git a/src/mathed/MathParser.cpp b/src/mathed/MathParser.cpp
index 83fc9c7..ca2eb0f 100644
--- a/src/mathed/MathParser.cpp
+++ b/src/mathed/MathParser.cpp
@@ -1785,7 +1785,7 @@ bool Parser::parse1(InsetMathGrid & grid, unsigned flags,
                                        break;
                        }
                        if (s.empty())
-                               cell->push_back(MathAtom(new InsetMathKern));
+                               cell->push_back(MathAtom(new MathMacro(buf, 
t.cs())));
                        else
                                cell->push_back(MathAtom(new InsetMathKern(s)));
                }