- added a NULL pointer test

- cosmetic changes

modules/gui/win32/preferences.cpp

@@ -268,6 +268,11 @@ __fastcall TPanelPlugin::TPanelPlugin( TComponent* Owner,
         ButtonDown->Hint = "Decrease the plugin priority";
         ButtonDown->ShowHint = true;
     }
+    else
+    {
+        ButtonUp = NULL;
+        ButtonDown = NULL;
+    }
 
     /* panel height */
     Height = CleanCheckListBox->Top + CleanCheckListBox->Height
@@ -284,8 +289,8 @@ void __fastcall TPanelPlugin::CheckListBoxClick( TObject *Sender )
      * started on an item */
     if( CleanCheckListBox->ItemIndex == -1 )
     {
-        ButtonUp->Enabled = false;
-        ButtonDown->Enabled = false;
+        if ( ButtonUp != NULL ) ButtonUp->Enabled = false;
+        if ( ButtonDown != NULL ) ButtonDown->Enabled = false;
         return;
     }
 
@@ -295,9 +300,7 @@ void __fastcall TPanelPlugin::CheckListBoxClick( TObject *Sender )
         return;
 
     /* enable up and down buttons */
-    if ( b_multi_plugins )
-    {
-        if ( CleanCheckListBox->ItemIndex != -1 )
+    if ( b_multi_plugins && ButtonUp != NULL && ButtonDown != NULL )
     {
         if ( CleanCheckListBox->ItemIndex == 0 )
             ButtonUp->Enabled = false; else ButtonUp->Enabled = true;
@@ -305,7 +308,6 @@ void __fastcall TPanelPlugin::CheckListBoxClick( TObject *Sender )
             == CleanCheckListBox->Items->Count - 1 )
             ButtonDown->Enabled = false; else ButtonDown->Enabled = true;
     }
-    }
 
     /* look for module 'Name' */
     list = vlc_list_find( p_intf, VLC_OBJECT_MODULE, FIND_ANYWHERE );