Fix focus crash in kart selection screen

data/gui/user_screen_tab.stkgui

@@ -16,12 +16,10 @@
 
         <box proportion="1" width="100%" layout="vertical-row">
 
-            <spacer height="15" width="10"/>
-
             <scrollable_ribbon id="players" height="120" y="10" x="10" width="98%" align="center" label_location="each"
                                square_items="true" child_width="128" child_height="128" />
 
-            <spacer height="15" width="10"/>
+            <spacer height="5" width="10"/>
             <div width="80%" align="center" layout="vertical-row" height="fit">
                 <div width="100%" height="fit" layout="horizontal-row" >
                     <label proportion="1" height="100%" text_align="left" I18N="In the user screen" text="Multiplayer Boost/Handicap"/>
@@ -52,7 +50,7 @@
                            I18N="In the user screen" text="Username"/>
                     <textbox id="username" proportion="2" height="fit" I18N="In the registration dialog"/>
                 </div>
-                <spacer height="20" width="20"/>
+                <spacer height="5" width="20"/>
 
                 <div width="100%" height="fit" layout="horizontal-row" >
                     <label id="label_password" proportion="1" height="100%" text_align="left"
@@ -63,7 +61,6 @@
             <div width="80%" align="center" layout="vertical-row" height="fit">
                 <label id="message" width="80%" align="center" text_align="left"/>
             </div>
-            <spacer width="20" height="25"/>
             <buttonbar id="options" width="90%" height="13%" align="center">
                 <icon-button id="ok" width="64" height="64" icon="gui/green_check.png"
                              I18N="Login dialog" text="OK" label_location="bottom"/>

src/guiengine/widgets/player_kart_widget.cpp

@@ -28,7 +28,6 @@
 #include "states_screens/kart_selection.hpp"
 #include <IGUIEnvironment.h>
 
-static int g_root_id;
 static const char RANDOM_KART_ID[] = "randomkart";
 
 using namespace GUIEngine;

src/states_screens/kart_selection.cpp

@@ -53,7 +53,7 @@ static const char ID_LOCKED[] = "locked/";
 //DEFINE_SCREEN_SINGLETON( KartSelectionScreen );
 KartSelectionScreen* KartSelectionScreen::m_instance_ptr = NULL;
 
-static int g_root_id;
+int g_root_id;
 
 /** Currently, navigation for multiple players at the same time is implemented
     in a somewhat clunky way. An invisible "dispatcher" widget is added above

src/states_screens/kart_selection.hpp

@@ -39,6 +39,8 @@ namespace Online
 class InputDevice;
 class KartHoverListener;
 
+extern int g_root_id;
+
 /**
   * \brief screen where players can choose their kart
   * \ingroup states_screens