Comment 5 for bug 1061967

While checking some changes today with valgrind (branch lp988601, rev 11717) I found a very large number of these reported:

==21335== Conditional jump or move depends on uninitialised value(s)
==21335== at 0x828C040: Inkscape::Text::Layout::Calculator::_computeFontLineHeight(font_instance*, double, SPStyle const*, Inkscape::Text::Layout::Lin
eHeight*, double*) (Layout-TNG-Compute.cpp:986)
==21335== by 0x828D0CA: Inkscape::Text::Layout::Calculator::_buildSpansForPara(Inkscape::Text::Layout::Calculator::ParagraphInfo*) const (Layout-TNG-C
ompute.cpp:1157)
==21335== by 0x828F0CA: Inkscape::Text::Layout::Calculator::calculate() (Layout-TNG-Compute.cpp:1473)
==21335== by 0xCDBBF0F: ???

line 986 is the last line in the following

    // yet another borked SPStyle member that we're going to have to fix ourselves
    for ( ; ; ) {
        if (style->line_height.set && !style->line_height.inherit) {
            if (style->line_height.normal)
                break;
            switch (style->line_height.unit) {