b2d: protect against empty clip region
b2d: protect against empty clip region

fniephaus/SqueakJS,bertfreudenberg/SqueakJS,fniephaus/SqueakJS,bertfreudenberg/SqueakJS,Speed-Pad/online,fniephaus/SqueakJS,the-impossible-quiz-revisited/the-impossible-quiz-revisited.github.io,the-impossible-quiz-revisited/the-impossible-quiz-revisited.github.io,Speed-Pad/online,sebastianconcept/SqueakJS,the-impossible-quiz-revisited/the-impossible-quiz-revisited.github.io,the-impossible-quiz-revisited/the-impossible-quiz-revisited.github.io,sebastianconcept/SqueakJS,fmateoc/SqueakJS,fmateoc/SqueakJS,fniephaus/SqueakJS,Speed-Pad/online,sebastianconcept/SqueakJS,fmateoc/SqueakJS,fmateoc/SqueakJS,bertfreudenberg/SqueakJS,bertfreudenberg/SqueakJS