[xy_grid] made -1 seed fixing apply to Var. seed too

scripts/xy_grid.py

@@ -218,7 +218,7 @@ class Script(scripts.Script):
         ys = process_axis(y_opt, y_values)
 
         def fix_axis_seeds(axis_opt, axis_list):
-            if axis_opt.label == 'Seed':
+            if axis_opt.label == 'Seed' or 'Var. seed':
                 return [int(random.randrange(4294967294)) if val is None or val == '' or val == -1 else val for val in axis_list]
             else:
                 return axis_list