zenno: allow both stats in threshold modifier to be null

zenno/src/lib/race.ts

@@ -275,7 +275,13 @@ export function adjustedStat(
 	}
 }
 
-export function thresholdMod(stat1: number, stat2?: number): number {
+export function thresholdMod(stat1: number | null | undefined, stat2?: number | null): number {
+	if (stat1 == null) {
+		if (stat2 == null) {
+			return 1;
+		}
+		return thresholdMod(stat2);
+	}
 	if (stat2 != null) {
 		return 0.5 * (thresholdMod(stat1) + thresholdMod(stat2));
 	}

zenno/src/routes/race/carryover/+page.svelte

@@ -255,6 +255,10 @@
 				<option value={per}>{per > 0 ? `Uphill +${per}` : per < 0 ? `Downhill ${per}` : 'Flat'}</option>
 			{/each}
 		</select>
+		<div class="col-span-full mx-2 mb-4 flex gap-4">
+			<label for="threshMod" class="my-auto flex-1">Track Threshold Mod</label>
+			<input type="number" id="threshMod" bind:value={threshMod} min="1.0" max="1.2" step="0.025" class="my-auto flex-1" />
+		</div>
 	</div>
 
 	<div class="mb-auto flex w-full max-w-4xl flex-col rounded-md text-center shadow-md ring md:col-span-6">
@@ -366,7 +370,7 @@
 	</table>
 {/snippet}
 <div class="mx-auto mt-8 grid max-w-4xl grid-cols-1 gap-8 md:grid-cols-2">
-	{@render seggsTable(slope < 0 && allowDAM ? 'Fastest Speed (Downhill)' : 'Fastest Speed', seggs[1])}
+	{@render seggsTable('Fastest Speed', seggs[1])}
 	{@render seggsTable('Slowest Speed', seggs[0])}
 </div>