don't ignore blocks that only have fields with object-type value

[i-just]

Description

Fixes an issue where a matrix block/nested entry is wrongly deemed as empty when the only data imported into it is, e.g. date.

Related issues

#1707

[jamesmacwhite]

I can confirm this bug also happens when the fields within the matrix block are just time fields. However, a workaround is add another field e.g. plain text and add some data like an random string or ID to the field layout, then the blocks will be created without issues.

Edit: This appears to only partially workaround the issue, it still appears that if the data being imported contains multiple items as an array only the first item is imported, however switching to another field type entirely such as plain text works.