[LyX/2.2.x] Fix problem noticed by Scott.

[Richard Heck]

commit 612dc74f75861784059d69059301e5505d34d65f
Author: Richard Heck <rgh...@lyx.org>
Date:   Tue Aug 2 18:54:31 2016 -0400

    Fix problem noticed by Scott.
    
    (cherry picked from commit 16d39b1f83253ff039c3db23124a74c02994e231)
---
 src/mathed/InsetMathGrid.cpp |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/src/mathed/InsetMathGrid.cpp b/src/mathed/InsetMathGrid.cpp
index e504494..a236a93 100644
--- a/src/mathed/InsetMathGrid.cpp
+++ b/src/mathed/InsetMathGrid.cpp
@@ -1248,6 +1248,7 @@ void InsetMathGrid::validate(LaTeXFeatures & features) 
const
                        "border-left: thin solid black; vertical-align: middle; 
padding-left: 0.5ex;}\n"
                        "table.mathtable td {text-align: left; border: none;}");
        }
+       InsetMathNest::validate(features);
 }