Update BufferUtils.java

android devices(like nexus 5) change to ART mode, creating a zero size bytebuffer will cause a crash, and ShapeRenderer will need a zero size buffer

the logs:
"F/art     ( 5062): art/runtime/check_jni.cc:64] JNI DETECTED ERROR IN APPLICATION: capacity must be greater than 0: 0
F/art     ( 5062): art/runtime/check_jni.cc:64]     in call to NewDirectByteBuffer
F/art     ( 5062): art/runtime/check_jni.cc:64]     from java.nio.ByteBuffer com.badlogic.gdx.utils.BufferUtils.newDisposableB                                                                                  yteBuffer(int)
"