Handle bounding box when cairo_fill_extents returns 0, 0, 0, 0
This messed up the bounding box causing issues when using rsvg_handle_render_element to render a single element.
Closes #1037 (closed)
This messed up the bounding box causing issues when using rsvg_handle_render_element to render a single element.
Closes #1037 (closed)