encoder_example: fail earlier on invalid picture size
encoder_example: fail earlier on invalid picture size

ycho/daala,xiph/daala,xiph/daala,ycho/daala,luctrudeau/daala,luctrudeau/daala,xiph/daala,luctrudeau/daala,xiph/daala,ycho/daala,ycho/daala,ycho/daala,luctrudeau/daala,luctrudeau/daala,xiph/daala