Print3D: Fix (unreported) error in Make Manifold tool

Remove redundant boundary fill step which gave the error when there was no boundary selected. Make sides property default to 0 so fill holes will cover for boundary fill absence.

object_print3d_utils/operators.py

@@ -434,7 +434,7 @@ class MESH_OT_Print3D_Clean_Non_Manifold(Operator):
     sides: bpy.props.IntProperty(
         name="sides",
         description="Number of sides in hole required to fill",
-        default=4,
+        default=0,
     )
 
     def execute(self, context):
@@ -553,10 +553,6 @@ class MESH_OT_Print3D_Clean_Non_Manifold(Operator):
         bpy.ops.mesh.select_all(action='SELECT')
         bpy.ops.mesh.fill_holes(sides=sides)
 
-        # fill selected edge faces, which could be additional holes
-        cls.select_non_manifold_verts(use_boundary=True)
-        bpy.ops.mesh.fill()
-
     @classmethod
     def delete_newly_generated_non_manifold_verts(cls):
         """delete any newly generated vertices from the filling repair"""