Divide by 0 when image is fully black

[pablojr]

Accidentally the leather cover was over the camera lens, so the image was fully black, and the embedding process ended up throwing an exception:

D/***************** JPEG-STEGO ******************(17749): Embedding of 1432 bits (175+4 bytes) 
D/***************** JPEG-STEGO ******************(17749): using default code, file will not fit
D/***************** JPEG-STEGO ******************(17749): 4 coefficients examined
E/***************** JPEG-STEGO ******************(17749): java.lang.ArithmeticException: divide by zero
W/System.err(17749): java.lang.ArithmeticException: divide by zero
W/System.err(17749):    at james.JpegEncoder.WriteCompressedData(JpegEncoder.java:577)
W/System.err(17749):    at james.JpegEncoder.Compress(JpegEncoder.java:93)
W/System.err(17749):    at james.JpegEncoder.Compress(JpegEncoder.java:113)
W/System.err(17749):    at info.guardianproject.f5android.Embed.<init>(Embed.java:84)
W/System.err(17749):    at info.guardianproject.f5android.Embed.<init>(Embed.java:41)
W/System.err(17749):    at com.mayorante.ztegocam.F5Embedder.doF5(F5Embedder.java:79)
W/System.err(17749):    at com.mayorante.ztegocam.F5Embedder.embed(F5Embedder.java:63)
W/System.err(17749):    at dalvik.system.NativeStart.run(Native Method)

[harlo]

great catch, thanks!