Fixed lines not be highlighted sometimes

[danipen]

Fixed a condition that caused that some lines were not highlighted until they were re-created.

• Open a document of, let's say 500 lines and go to line 400 (visible range is 400-450).
• Open a document of 100 lines (first line is visible).
• When the TMModel starts to emit tokens, the visual lines haven't been constructed yet.

So _firstVisibleLineIndex and _lastVisibleLineIndex are not updated and still 400 and 450. So this condition avoids not post to the dispatcher the redraw

    bool changedLinesAreNotVisible =
        (firstChangedLineIndex < _firstVisibleLineIndex && lastChangedLineIndex < _firstVisibleLineIndex) ||
        (firstChangedLineIndex > _lastVisibleLineIndex && lastChangedLineIndex > _lastVisibleLineIndex);

        if (changedLinesAreNotVisible)
            return;

Solution:
Just initialize control a flag _areVisualLinesValid and check it to calculate if changedLinesAreNotVisible.
Otherwise, post all the redraw events to the dispatcher to ensure that lines are redrawn after transforming them.

[miryamGSM]

LGTM