Revert "wmapro: prevent division by zero when sample rate is unspecified"

This reverts commit 36936080. It was
already applied; no idea why it didn't error out while re-applying it.

libavcodec/wmaprodec.c

@@ -340,11 +340,6 @@ static av_cold int decode_init(AVCodecContext *avctx)
         return AVERROR_INVALIDDATA;
     }
 
-    if (s->avctx->sample_rate <= 0) {
-        av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
-        return AVERROR_INVALIDDATA;
-    }
-
     s->num_channels = avctx->channels;
 
     if (s->num_channels < 0) {