obs-ffmpeg: Missing NVENC bounds check

plugins/obs-ffmpeg/jim-nvenc.c

@@ -491,13 +491,16 @@ static bool init_encoder(struct nvenc_data *enc, obs_data_t *settings)
 	enc->output_delay = output_delay;
 
 	if (lookahead) {
-		int lkd_bound = output_delay - config->frameIntervalP - 4;
-
-		config->rcParams.enableLookahead = 1;
-		config->rcParams.lookaheadDepth =
-			max(enc->rc_lookahead, lkd_bound);
-		config->rcParams.disableIadapt = 0;
-		config->rcParams.disableBadapt = 0;
+		const int lkd_bound = output_delay - config->frameIntervalP - 4;
+		if (lkd_bound >= 0) {
+			config->rcParams.enableLookahead = 1;
+			config->rcParams.lookaheadDepth =
+				max(enc->rc_lookahead, lkd_bound);
+			config->rcParams.disableIadapt = 0;
+			config->rcParams.disableBadapt = 0;
+		} else {
+			lookahead = false;
+		}
 	}
 
 	/* psycho aq */