Fall back to default vim behavior after first visual selection

This commit fixes a couple of issues:
* Chaining `i{` after the initial `vi{` doesn't work very well. Eg, `vi{i{` does not expand after the intial selection.
* Chaining `i{` doesn't work at all if `virtualedit=all` and the last `}` is preceded by a tab.

The vim default behavior is a good fall back for *chaining* `i{` (and other "default" text objects). This change only affects `i`, not `a`.