avcodec/wmaprodec: Fix integer overflow in sfb_offsets initialization

Fixes out of array read
Fixes: asan_heap-oob_2aec5b0_1828_classical_22_16_2_16000_v3c_0_exclusive_0_29.wma
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/wmaprodec.c

@@ -422,6 +422,9 @@ static av_cold int decode_init(AVCodecContext *avctx)
             offset &= ~3;
             if (offset > s->sfb_offsets[i][band - 1])
                 s->sfb_offsets[i][band++] = offset;
+
+            if (offset >= subframe_len)
+                break;
         }
         s->sfb_offsets[i][band - 1] = subframe_len;
         s->num_sfb[i]               = band - 1;