Fix panic that occurs during setting min-voice-activity-ms property

[sungbin-lee]

There is a problem while setting min-voice-activity-ms property.
I confirmed it happens during execution: g_object_set(obj, "min-voice-activity-ms", value, NULL);

below is the error log.

thread '<unnamed>' panicked at src/filter/imp.rs:255:54:
called `Result::unwrap()` on an `Err` value: ValueTypeMismatchError { actual: gint, requested: guint64 }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
fatal runtime error: failed to initiate panic, error 5
./whisper.sh: line 9: 1025283 Aborted                 (core dumped) gst-launch-1.0 filesrc location=${FILE_NAME} ! decodebin3 name=demux demux.audio_0 ! queue ! audioconvert ! audioresample ! queue ! whisper language="auto" min-voice-activity-ms=120 ! fdsink