ffserver_config: check for INT_MIN before doing FFABS

FFABS(INT_MIN) is not safe. Alternative of using FFNABS is not as
readable.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>

ffserver_config.c

@@ -460,7 +460,7 @@ static int ffserver_set_int_param(int *dest, const char *value, int factor,
     if (tmp < min || tmp > max)
         goto error;
     if (factor) {
-        if (FFABS(tmp) > INT_MAX / FFABS(factor))
+        if (tmp == INT_MIN || FFABS(tmp) > INT_MAX / FFABS(factor))
             goto error;
         tmp *= factor;
     }