fix typing issue

Author: victorhuangwq

instrumentation-client.ts

@@ -1,14 +1,20 @@
-import posthog from "posthog-js"
+import posthog from "posthog-js";
 
-posthog.init(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
-	api_host: "/ingest",
-	ui_host: "https://us.posthog.com",
-	defaults: "2025-05-24",
-	capture_exceptions: true, // This enables capturing exceptions using Error Tracking
-	session_recording: {
-		// Prevent large base64 images from being serialized into recordings
-		blockClass: "ph-no-capture",
-		blockSelector: ".ph-no-capture",
-	},
-	debug: process.env.NODE_ENV === "development",
-});
+const posthogKey = process.env["NEXT_PUBLIC_POSTHOG_KEY"];
+
+if (posthogKey) {
+	posthog.init(posthogKey, {
+		api_host: "/ingest",
+		ui_host: "https://us.posthog.com",
+		defaults: "2025-05-24",
+		capture_exceptions: true, // This enables capturing exceptions using Error Tracking
+		session_recording: {
+			// Prevent large base64 images from being serialized into recordings
+			blockClass: "ph-no-capture",
+			blockSelector: ".ph-no-capture",
+		},
+		debug: process.env.NODE_ENV === "development",
+	});
+} else if (process.env.NODE_ENV === "development") {
+	console.warn("PostHog: NEXT_PUBLIC_POSTHOG_KEY is not defined");
+}