obs-ffmpeg: Fix warning and remove unnecessary null checks

The if statement erroneously ended with a ';', which means that the code
is always executed, but there's no reason to even have these if checks
in the first place as the functions themselves return safely with null
pointers.

plugins/obs-ffmpeg/obs-ffmpeg-nvenc.c

@@ -192,10 +192,8 @@ static void nvenc_destroy(void *data)
 {
 	struct nvenc_encoder *enc = data;
 
-	if (enc->context)
-		avcodec_close(enc->context);
-	if (enc->vframe);
-		av_frame_free(&enc->vframe);
+	avcodec_close(enc->context);
+	av_frame_free(&enc->vframe);
 	avpicture_free(&enc->dst_picture);
 	da_free(enc->buffer);
 	bfree(enc->header);