Added wxPropertyGrid::GetUnspecifiedValueText(). Use it instead of assuming that the unspecified value text is always an empty string.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62955 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/propgrid/propgrid.h

@@ -740,6 +740,14 @@ public:
     */
     wxTextCtrl* GetEditorTextCtrl() const;
 
+    /**
+        Returns (visual) text representation of the unspecified
+        property value.
+
+        @param argFlags For internal use only.
+    */
+    wxString GetUnspecifiedValueText( int argFlags = 0 ) const;
+
     /**
         Returns current vertical spacing.
     */