Previewing product kit after change causes "Trying to get property of non-object"

I edited an existing product kit.

I removed one item, added a different item, and did "Save and continue."

I modified the list position of the new item and clicked "Preview".

Hundreds of error messages popped up, along the lines of....

• Notice: Trying to get property of non-object in uc_product_kit_view() (line 737 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.module).
• Notice: Trying to get property of non-object in theme_uc_product_kit_list_item() (line 55 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.theme.inc).
• Notice: Trying to get property of non-object in theme_uc_product_kit_list_item() (line 60 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.theme.inc).
• Notice: Trying to get property of non-object in theme_uc_product_kit_list_item() (line 63 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.theme.inc).
• Notice: Trying to get property of non-object in uc_product_kit_view() (line 740 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.module).

....

• Notice: Trying to get property of non-object in uc_product_kit_view() (line 740 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.module).
• Notice: Trying to get property of non-object in uc_product_kit_form() (line 560 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.module).
• Notice: Trying to get property of non-object in uc_product_kit_form() (line 566 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.module).
• Notice: Trying to get property of non-object in uc_product_kit_form() (line 580 of .../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.module).
• Notice: Trying to get property of non-object in uc_product_kit_form() (line 584 of.../sites/all/modules/ubercart/uc_product_kit/uc_product_kit.module).

...and the form for setting the list position, discount, and quantity is all messed up.

See #1701022: Notice: Undefined property: stdClass::$price in uc_product_view() when previewing new product and #1677876: Trying to get property of non-object in uc_product_kit_update() when adding extra products to a kit for similar issues.