[LyX/master] Make a false positive explicit

[Jean-Marc Lasgouttes]

commit 000dcb8672b68a6366ee48ce88c3adb57adecfd1
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Wed Mar 8 16:50:03 2017 +0100

    Make a false positive explicit
    
    Pleases coverity
---
 src/mathed/MathData.cpp |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/src/mathed/MathData.cpp b/src/mathed/MathData.cpp
index 9d21898..8ff9461 100644
--- a/src/mathed/MathData.cpp
+++ b/src/mathed/MathData.cpp
@@ -825,7 +825,10 @@ void MathData::collectParameters(Cursor * cur,
                }
 
                // put cursor in argument again
-               if (thisSlice != - 1 && thisPos == int(pos)) {
+               // Note: The first two expressions on the first line are
+               // equivalent (see caller), but making this explicit pleases
+               // coverity.
+               if (cur && thisSlice != -1 && thisPos == int(pos)) {
                        cur->append(params.size() - 1, argPos);
                        cur->append(argSlices);
                        (*cur)[thisSlice].pos() = macroPos;