Prevent users from creating accounts with a blank email address

Handle empty email strings by setting them to null to avoid database constraint errors in `server/storage.ts`.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: dec54137-d5a2-4406-8ad4-5f2f9fb110bf
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/0715008c-7244-40f4-befc-26c014852236/56f97713-69fd-41d1-b933-ff4440458da0.jpg

server/storage.ts

@@ -60,6 +60,11 @@ export class DatabaseStorage implements IStorage {
       userData.password = await this.hashPassword(userData.password);
     }
     
+    // Convert empty email to null to avoid unique constraint issues
+    if (userData.email === "") {
+      userData.email = null;
+    }
+    
     const [user] = await db
       .insert(users)
       .values(userData)
@@ -73,6 +78,11 @@ export class DatabaseStorage implements IStorage {
       userData.password = await this.hashPassword(userData.password);
     }
     
+    // Convert empty email to null to avoid unique constraint issues
+    if (userData.email === "") {
+      userData.email = null;
+    }
+    
     const [user] = await db
       .update(users)
       .set(userData)