Make subtitle optional

components/SectionHeader.tsx

@@ -4,14 +4,14 @@ import styles from "./SectionHeader.module.css";
 
 interface SectionHeaderProps {
   title: string;
-  subtitle: string;
+  subtitle?: string;
 }
 
 export function SectionHeader({ title, subtitle }: SectionHeaderProps) {
   return (
     <div className={styles.header}>
       <h1 className={styles.title}>{title}</h1>
-      <h5 className={styles.subTitle}>{subtitle}</h5>
+      {subtitle && <h5 className={styles.subTitle}>{subtitle}</h5>}
     </div>
   );
 }