RA144: work around gcc bug/oddity on ARM

This should not make any difference, yet some gcc versions on ARM
produce incorrect output without this fix.

Approved by Vitor.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@17698 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/ra144.c

@@ -200,7 +200,7 @@ static void do_output_subblock(RA144Context *ractx, const uint16_t  *lpc_coefs,
 
     block = ractx->adapt_cb + BUFFERSIZE - BLOCKSIZE;
 
-    add_wav(block, gain, cba_idx, m, buffer_a,
+    add_wav(block, gain, cba_idx, m, cba_idx? buffer_a: NULL,
             cb1_vects[cb1_idx], cb2_vects[cb2_idx]);
 
     memcpy(ractx->curr_sblock, ractx->curr_sblock + 40,