accepting a line in isearch does not remove cursor imprint and partial path highlighting

[m0vie]

When accepting a line from within an isearch minimuffer, none of the accept-* widgets are called so the special handling for cursor imprint and partial path removal is not triggered.

Should use zle-line-finish instead.

[danielshahaf]

Reproduction instructions at #259 (comment)

[danielshahaf]

PR: #288