Correcting Tcl update

After upgrading to the newest Linux distribution program fitexex stopped working due to incorrectly reported error.
"_tkinter.TclError: cannot use geometry manager grid inside . which already has slaves managed by pack"
The fitexex has been solely using grid() manager since the beginning but in the new Tcl creation of Toolbar
self.toolbar = NavigationToolbar2TkAgg(self.canvas, self)
seems to require immediate 
self.toolbar.grid().
In the old version it was possible to defer the grid() until all the widgets were created.
Here it seems like the Toolbar is using pack() by default, therefore causing this error.
Added one line to correct it.