Fix TokenCompleteTextView's "prevent free-form text" behavior

[cketti]

Fixes a bug that was introduced in 11b989e.

The code

if (preventFreeFormText || currentCompletionText().length() > 0) {
    // do thing
}

was replaced with

if (currentCompletionText().length() > 0) {
    // do thing
}

when it should have been

// do thing

because preventFreeFormText was always true.

Fixes #8732 (issue also contains instructions on how to reproduce)