Replaces references to wxT("") with wxEmptyString in propgrid sample.

samples/propgrid/propgrid.cpp

@@ -1305,7 +1305,7 @@ void FormMain::PopulateWithExamples ()
     soc.Add( wxT("Look, it continues"), 200 );
     soc.Add( wxT("Even More"), 240 );
     soc.Add( wxT("And More"), 280 );
-    soc.Add( wxT(""), 300 );
+    soc.Add( wxEmptyString, 300 );
     soc.Add( wxT("True End of the List"), 320 );
 
     // Test custom colours ([] operator of wxPGChoices returns

samples/propgrid/tests.cpp

@@ -92,7 +92,7 @@ public:
                                      int argFlags = 0 ) const wxOVERRIDE
     {
         if ( index == (int)(m_choices.GetCount()-1) )
-            return wxT("");
+            return wxEmptyString;
 
         return wxColourProperty::ColourToString(col, index, argFlags);
     }