avcodec/jpeglsdec: check err value for ls_get_code_runterm()

Fixes infinite loop
Fixes Ticket3086

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

libavcodec/jpeglsdec.c

@@ -148,6 +148,8 @@ static inline int ls_get_code_runterm(GetBitContext *gb, JLSState *state,
         ret = ret >> 1;
     }
 
+    if(FFABS(ret) > 0xFFFF)
+        return -0x10000;
     /* update state */
     state->A[Q] += FFABS(ret) - RItype;
     ret         *= state->twonear;