Improve redirect to entry n case the entry has been deleted.

See #39 (comment) for details.

src/Admin.php

@@ -202,33 +202,38 @@ public static function custom_merge_tags( $merge_tags ) {
 	}
 
 	/**
-	 * Maybe redirect to Gravity Forms entry
+	 * Maybe redirect to Gravity Forms entry.
+	 * 
+	 * @return void
 	 */
 	public static function maybe_redirect_to_entry() {
 		// phpcs:ignore WordPress.Security.NonceVerification.Recommended
-		$lead_id = \array_key_exists( 'pronamic_gf_lid', $_GET ) ? \sanitize_text_field( \wp_unslash( $_GET['pronamic_gf_lid'] ) ) : null;
-
-		if ( null === $lead_id ) {
+		if ( ! \array_key_exists( 'pronamic_gf_lid', $_GET ) ) {
 			return;
 		}
 
+		// phpcs:ignore WordPress.Security.NonceVerification.Recommended
+		$lead_id = \sanitize_text_field( \wp_unslash( $_GET['pronamic_gf_lid'] ) );
+
 		$lead = RGFormsModel::get_lead( $lead_id );
 
-		if ( ! empty( $lead ) ) {
-			$url = add_query_arg(
-				[
-					'page' => 'gf_entries',
-					'view' => 'entry',
-					'id'   => $lead['form_id'],
-					'lid'  => $lead_id,
-				],
-				admin_url( 'admin.php' )
-			);
+		if ( false === $lead ) {
+			\wp_die( \esc_html__( 'The requested Gravity Forms entry could not be found.', 'pronamic_ideal' ) );
+		}
 
-			wp_safe_redirect( $url );
+		$url = \add_query_arg(
+			[
+				'page' => 'gf_entries',
+				'view' => 'entry',
+				'id'   => $lead['form_id'],
+				'lid'  => $lead_id,
+			],
+			admin_url( 'admin.php' )
+		);
 
-			exit;
-		}
+		wp_safe_redirect( $url );
+
+		exit;
 	}
 
 	/**