prevents empty text from being rendered

Computing a bounding box on https://github.com/rctoris/ros3djs/compare/RobotWebTools:develop...develop#diff-ed07448aa3074b47ea2aa22b6bd8b70fL235 causes an error if the empty string was rendered. This prevents any empty strings from being "displayed."
Oh of course.  It was not obvious in my browser.  :)