Editing assist has different behavior depending on whitespace

## Steps to Reproduce

1. Create a new project
1. Move to line 76, place the cursor inside `Text` and press Alt-Enter
1. Select the 'Wrap' assist
1. Enter `Ro` and press Tab to complete to `Row`

=> Cursor moves to 'child', and 'child' is in a red box suggesting you have to complete it

1. Close project. Create a new project
1. Move to line 79, place the cursor inside `Text` and press Alt-Enter
1. Select the 'Wrap' assist
1. Enter `Ro` and press Tab to complete to `Row`

=> Cursor moves to right after `Row(`. Subsequent Tab presses just adds empty tabs stops

## Version info

Flutter plugin version 12 in IDEA version 2017.1 on Windows.