Focus snakview variation only when viewState is enabled

Fixes issues with main snak value disappearing when
saving qualifiers, setting rank, and javascript
freezing / throwing errors, and other related issues.

When snakview variation value view / viewState is disabled,
the qualifier and/or main snak value may become null and
cause these issues when saving.

This preserves focus behaviour when selecting a property,
then autofocusing on the value.

Bug: 64651
Bug: 65694
Bug: 65693
Bug: 65398
Change-Id: I0f39f7500597f8e1488d922ab115199d92399ecb
(cherry picked from commit 4751b1b8b58a7c82c0e4398672aa38612f197685)