plugins/vala-indenter: Fix bug in indenter with stripped EOLs

This fixes a bug that yield wrong indentation:

<2tab>try {
<3tab    >foo ();
<2tab>} catch (...) {
<emptyAsLinesAreStripped>
<2tab>}
<2tab>foo ();<Press ENTER here>

This would end up at one tab, or one indentation level less than the last foo()

I tested it by dropping f126acac058caa3d5c869d68e85842cd7ba76bc8, it compiled and was tested successfully