avutil/opt: only skip evaluation for rational options

Fixes problems when non-rational options were set using rational expressions,
causing rounding errors and the option range limits not to be enforced
properly.

ffmpeg -f lavfi -i "sine=r=96000/2"

This caused an assertion failure with assert level 2.
Signed-off-by: Marton Balint <cus@passwd.hu>

libavutil/opt.c

@@ -229,14 +229,16 @@ static int set_string(void *obj, const AVOption *o, const char *val, uint8_t **d
 static int set_string_number(void *obj, void *target_obj, const AVOption *o, const char *val, void *dst)
 {
     int ret = 0;
+
+    if (o->type == AV_OPT_TYPE_RATIONAL || o->type == AV_OPT_TYPE_VIDEO_RATE) {
         int num, den;
         char c;
-
         if (sscanf(val, "%d%*1[:/]%d%c", &num, &den, &c) == 2) {
             if ((ret = write_number(obj, o, dst, 1, den, num)) >= 0)
                 return ret;
             ret = 0;
         }
+    }
 
     for (;;) {
         int i = 0;