Fix warning

Author: fzaninotto

src/contacts/ContactInputs.tsx

@@ -129,7 +129,10 @@ const ContactPersonalInformationInputs = () => {
         if (first_name || last_name || !email) return;
         const [first, last] = email.split('@')[0].split('.');
         setValue('first_name', first.charAt(0).toUpperCase() + first.slice(1));
-        setValue('last_name', last.charAt(0).toUpperCase() + last.slice(1));
+        setValue(
+            'last_name',
+            last ? last.charAt(0).toUpperCase() + last.slice(1) : ''
+        );
     };
 
     const handleEmailPaste: React.ClipboardEventHandler<HTMLDivElement> = e => {