dirac: fix inverted check

Regression since: ea6da80c
Fixes Ticket2123

I cannot reproduce any regressions by flipping the wrong condition
to how it should have been.

Thanks-to: ubitux
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/dirac.c

@@ -237,7 +237,7 @@ static int parse_source_parameters(AVCodecContext *avctx, GetBitContext *gb,
 
     avctx->pix_fmt = dirac_pix_fmt[!luma_offset][source->chroma_format];
     avcodec_get_chroma_sub_sample(avctx->pix_fmt, &chroma_x_shift, &chroma_y_shift);
-    if (!(source->width % (1<<chroma_x_shift)) || !(source->height % (1<<chroma_y_shift))) {
+    if ((source->width % (1<<chroma_x_shift)) || (source->height % (1<<chroma_y_shift))) {
         av_log(avctx, AV_LOG_ERROR, "Dimensions must be a integer multiply of the chroma subsampling\n");
         return AVERROR_INVALIDDATA;
     }