fix: disable button when marker is not present

src/routes/+page.svelte

@@ -88,9 +88,11 @@
 </script>
 
 <div class="container">
-	<span class="title">{data.gameData.stopName}</span>
+	<h1>{data.gameData.stopName}</h1>
 
-	<div hidden={submitted}><button onclick={checkLocation}>SUBMIT</button></div>
+	<div hidden={submitted}>
+		<button onclick={checkLocation} disabled={latlng.lat === 0 || latlng.lng === 0}>SUBMIT</button>
+	</div>
 
 	<div class="results" hidden={!submitted}>
 		{Math.floor(points)} points! Vous etiez à {Math.floor(distance)}m.
@@ -117,11 +119,6 @@
 		text-align: center;
 	}
 
-	.title {
-		font-weight: bold;
-		font-size: 32px;
-	}
-
 	.results {
 		color: green;
 		font-size: 20px;