avcodec/pictordec: run av_image_check_size() unconditionally

This ensures that no invalid size leaks through
(This issue is hypothetical, ive no testcase)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/pictordec.c

@@ -140,9 +140,9 @@ static int decode_frame(AVCodecContext *avctx,
 
     avctx->pix_fmt = AV_PIX_FMT_PAL8;
 
+    if (av_image_check_size(s->width, s->height, 0, avctx) < 0)
+        return -1;
     if (s->width != avctx->width && s->height != avctx->height) {
-        if (av_image_check_size(s->width, s->height, 0, avctx) < 0)
-            return -1;
         avcodec_set_dimensions(avctx, s->width, s->height);
     }