Use empty() member function to determine if arrays are empty in wxPG.

Use this dedicated function instead of checking if size() function returns zero/non-zero value.

src/propgrid/props.cpp

@@ -1207,7 +1207,7 @@ wxEnumProperty::wxEnumProperty( const wxString& label, const wxString& name,
 {
     SetIndex(0);
 
-    if ( &labels && labels.size() )
+    if ( &labels && !labels.empty() )
     {
         m_choices.Set(labels, values);
 
@@ -1595,7 +1595,7 @@ wxFlagsProperty::wxFlagsProperty( const wxString& label, const wxString& name,
 {
     m_oldChoicesData = NULL;
 
-    if ( &labels && labels.size() )
+    if ( &labels && !labels.empty() )
     {
         m_choices.Set(labels,values);