Fix: Spell checker cannot be re-enabled.

Without this CL, preference for enabling spell checking is disabled
when spell checking is disabled.
This issue makes it impossible to re-enable spell checking from the
settings UI.
This was introduced in I0ed71bbb580e3547d97e321799ac2b77b1f284a3
that fixes Bug: 26685795.

Bug: 28157871
Change-Id: I386baf2dd79347c1202f885a3f749aea3fb6a58d
1 file changed