Timeline: Hide spacer widget that was interfering with drag and drop event delivery.

Closes #165

timeline/src/Timeline.C

@@ -751,7 +751,10 @@ Timeline::Timeline ( int X, int Y, int W, int H, const char* L ) : BASE( X, Y, W
             panzoomer = o;
         }
 
+        /* this is used to define the sizing limits of the enclosing Fl_Tile */
         Fl_Box *spacebox = new Fl_Box( 0,0,1,1 );
+        /* doesn't need to be visible */
+        spacebox->hide();
 
         o->end();
         o->resizable( spacebox );