wmalosslessdec: avoid reading 0 bits with get_bits

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
(cherry picked from commit f9020d51)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/wmalosslessdec.c

@@ -486,7 +486,7 @@ static int decode_cdlms(WmallDecodeCtx *s)
                 if ((1 << cbits) < s->cdlms[c][i].scaling + 1)
                     cbits++;
 
-                s->cdlms[c][i].bitsend = get_bits(&s->gb, cbits) + 2;
+                s->cdlms[c][i].bitsend = (cbits ? get_bits(&s->gb, cbits) : 0) + 2;
                 shift_l = 32 - s->cdlms[c][i].bitsend;
                 shift_r = 32 - s->cdlms[c][i].scaling - 2;
                 for (j = 0; j < s->cdlms[c][i].coefsend; j++)