[LyX/2.3.x] Use proper localization chain for Box special width/height

[Juergen Spitzmueller]

commit d65eee368874b07851e97cc5a70bac65f95f7c28
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Sat Jan 27 12:26:01 2018 +0100

    Use proper localization chain for Box special width/height
    
    Fixes: #11000
    (cherry picked from commit e2160ec960de2f48e5b61dfab339902426d075f8)
---
 src/frontends/qt4/GuiBox.cpp |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/frontends/qt4/GuiBox.cpp b/src/frontends/qt4/GuiBox.cpp
index 8a6763e..3d1010b 100644
--- a/src/frontends/qt4/GuiBox.cpp
+++ b/src/frontends/qt4/GuiBox.cpp
@@ -439,7 +439,7 @@ docstring GuiBox::dialogToParams() const
                if (ids_spec_.contains(unit) && 
!isValidLength(fromqstr(value))) {
                        params.special = fromqstr(unit);
                        // Note: the unit is simply ignored in this case
-                       params.width = Length(value.toDouble(), Length::IN);
+                       params.width = Length(widgetToDouble(widthED), 
Length::IN);
                } else {
                        params.special = "none";
                        // we must specify a valid length in this case
@@ -465,7 +465,7 @@ docstring GuiBox::dialogToParams() const
                if (ids_spec_.contains(unit) && 
!isValidLength(fromqstr(value))) {
                        params.height_special = fromqstr(unit);
                        // Note: the unit is simply ignored in this case
-                       params.height = Length(value.toDouble(), Length::IN);
+                       params.height = Length(widgetToDouble(heightED), 
Length::IN);
                } else {
                        params.height_special = "none";
                        params.height =