Handle unique session errors.

lib/session.js

@@ -37,16 +37,22 @@ export async function getSession(req) {
   let session = await getSessionByUuid(session_uuid);
 
   if (!session) {
-    session = await createSession(website_id, {
-      session_uuid,
-      hostname,
-      browser,
-      os,
-      screen,
-      language,
-      country,
-      device,
-    });
+    try {
+      session = await createSession(website_id, {
+        session_uuid,
+        hostname,
+        browser,
+        os,
+        screen,
+        language,
+        country,
+        device,
+      });
+    } catch (e) {
+      if (!e.message.includes('Unique constraint')) {
+        throw e;
+      }
+    }
   }
 
   const { session_id } = session;