Fix crash in receiveEmail when no R2 bucket binding is found

If no R2 bucket is configured via emailRouting.targetBucket and no
bucket binding exists in the environment, the email handler would
crash with a TypeError when calling bucket.put() on undefined.

This adds a guard that throws a descriptive error message instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: G4brym

.changeset/fix-receive-email-guard.md

@@ -0,0 +1,5 @@
+---
+"r2-explorer": patch
+---
+
+Add missing null check for R2 bucket in email handler to prevent crash when no bucket binding is found

packages/worker/src/modules/emails/receiveEmail.ts

@@ -46,6 +46,12 @@ export async function receiveEmail(
 		}
 	}
 
+	if (!bucket) {
+		throw new Error(
+			"No R2 bucket binding found for email routing. Configure emailRouting.targetBucket or add an R2 bucket binding.",
+		);
+	}
+
 	const rawEmail = await streamToArrayBuffer(event.raw, event.rawSize);
 	const parser = new PostalMime();
 	const parsedEmail = await parser.parse(rawEmail);