Fixed #35449 -- Fixed validation issue with SplitArrayField when remove_trailing_nulls=True

[saJaeHyukc]

Trac ticket number

ticket-35449

Branch description

The proposed changes ensure that trailing null values are correctly removed before validation occurs, and that errors are appropriately handled.

Checklist

• This PR targets the main branch.
• The commit message is written in past tense, mentions the ticket number, and ends with a period.
• I have checked the "Has patch" ticket flag in the Trac system.
• I have added or updated relevant tests.
• I have added or updated relevant docs, including release notes if applicable.
• I have attached screenshots in both light and dark modes for any UI changes.

[sarahboyce]

Thank you for this @saJaeHyukc!
I have a couple of comments 👍

[sarahboyce]

Suggested change

	field.clean(["abc", "", ""])
	self.assertEqual(
	cm.exception.messages,
	[
	"Item 1 in the array did not validate: Ensure this value has at most 2 "
	"characters (it has 3).",
	],
	)
	field.clean(["abc", "", "", ""])
	self.assertEqual(
	cm.exception.messages,
	[
	"Item 1 in the array did not validate: Ensure this value has at most 2 "
	"characters (it has 3).",
	"Item 2 in the array did not validate: This field is required.",
	"Item 3 in the array did not validate: This field is required.",
	],
	)

Sorry, I think the suggested test case wasn't exactly right.
I think because required=True we should have errors for missing Item 2 and 3 but because remove_trailing_nulls=True we can ignore that the list is too long 🤔