aacsbr: change order of operation to prevent out of array read

Fixes CID732250
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/aacsbr.c

@@ -555,7 +555,7 @@ static int sbr_hf_calc_npatches(AACContext *ac, SpectralBandReplication *sbr)
             k = sbr->n_master;
     } while (sb != sbr->kx[1] + sbr->m[1]);
 
-    if (sbr->patch_num_subbands[sbr->num_patches-1] < 3 && sbr->num_patches > 1)
+    if (sbr->num_patches > 1 && sbr->patch_num_subbands[sbr->num_patches-1] < 3)
         sbr->num_patches--;
 
     return 0;