Bug 689523: data bootstrap initial values in the text style editor at construction.

This was causing first a visual issue where the style editor UI would
show no default font/size/style at instanciation, but even a crash
when the user would change the font size or style (bold, italic...)
from this UI before selecting a font or writing a text.

app/widgets/gimptextstyleeditor.c

@@ -365,6 +365,8 @@ gimp_text_style_editor_constructed (GObject *object)
                          G_CALLBACK (gimp_text_style_editor_update),
                          editor, 0,
                          G_CONNECT_AFTER | G_CONNECT_SWAPPED);
+
+  gimp_text_style_editor_update (editor);
 }
 
 static void