[LyX/master] Handle correctly zero table special arguments.

[Juergen Spitzmueller]

commit fc9d47f7f488477ba09fe637b81af2356feef8c8
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Tue Jun 26 10:51:16 2018 +0200

    Handle correctly zero table special arguments.
    
    Fixes: #10247
---
 src/frontends/qt4/GuiTabular.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/frontends/qt4/GuiTabular.cpp b/src/frontends/qt4/GuiTabular.cpp
index 284bf87..4ac80ad 100644
--- a/src/frontends/qt4/GuiTabular.cpp
+++ b/src/frontends/qt4/GuiTabular.cpp
@@ -33,6 +33,7 @@
 
 #include "support/convert.h"
 #include "support/debug.h"
+#include "support/lstrings.h"
 
 #include <QCheckBox>
 #include <QPushButton>
@@ -576,7 +577,7 @@ docstring GuiTabular::dialogToParams() const
 
        // apply the special alignment
        string special = fromqstr(specialAlignmentED->text());
-       if (special.empty())
+       if (support::trim(special).empty())
                special = "none";
        if (multicolumnCB->isChecked())
                setParam(param_str, Tabular::SET_SPECIAL_MULTICOLUMN, special);