Empty string is null?

[hasen]

How to pass it to C functions that expect a non-null string? 
Specifically to GTK+ (using gtkD)

I also asked this on stackoverflow 
http://stackoverflow.com/questions/931360/

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Using D1 with phobos

I have a text entry field, instance of gtk.Entry.Entry,

calling setText("") raises a run time error

   Gtk-CRITICAL **: gtk_entry_set_text: assertion `text != NULL' failed

Why? It seems to be a problem with D, I tried this:

   string empty = "";
   assert (empty != null);
   my_entry.setText(empty)

The program terminated as the assertion failed.

How can I work around this?