views/month: Cancel active animation before starting new ones

Before, two finger scrolls on mint cinnamon (X11 scroll instead of
wayland) caused month view to crash. g_clear_obj... orphan would an
animation allowing two animations to exist at once, causing conflict
when the orphan continued in the background. The two animations would be
generated due to X11's legacy support of both discrete notch scrolling
and the two finger smooth scrolling.

I replaced g_clear... with cancel_row_offset_animation in
snap_to_top_row which ensures that the orphaned animation is dead prior
to reassigning variables.

Fixes: https://gitlab.gnome.org/GNOME/gnome-calendar/-/work_items/1616
Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/801>

src/gui/views/gcal-month-view.c

@@ -531,7 +531,7 @@ snap_to_top_row (GcalMonthView *self)
 
   animation_target = adw_callback_animation_target_new (animate_row_offset_cb, self, NULL);
 
-  g_clear_object (&self->row_offset_animation);
+  cancel_row_offset_animation (self);
   self->row_offset_animation = adw_timed_animation_new (GTK_WIDGET (self),
                                                         self->row_offset,
                                                         0.0,