Set json text box with selected field

Change-Id: I4f1a3551056642f422961370e435cba1db3ea9f0
diff --git a/frc971/control_loops/python/spline_graph.py b/frc971/control_loops/python/spline_graph.py
index 73f0460..f8955c6 100755
--- a/frc971/control_loops/python/spline_graph.py
+++ b/frc971/control_loops/python/spline_graph.py
@@ -113,7 +113,7 @@
         self.file_name_box = Gtk.Entry()
         self.file_name_box.set_size_request(200, 40)
 
-        self.file_name_box.set_text("output_file_name.json")
+        self.file_name_box.set_text(FIELD.json_name)
         self.file_name_box.set_editable(True)
 
         container.put(self.file_name_box, 0, 0)