Comment 8 for bug 1548953

The attached patch fixes this bug (tested on Windows 7 x64 with Inkscape 0.91+devel_64bit r14691).

Cause were uninitialized fields "left/right" of "Geom::OptRect tiltb" in the rare case of certain whitespace characters containing path data that results in an empty bounding box (e.g. a single move-to command).
Normal whitespace characters do *not* contain path data (therefore "_drawable = false" in the conditional) and therefore didn't trigger the bug.