Add MDTimelineNotAvailable

exceptions/page/MDTimelineNotAvailable.php

@@ -0,0 +1,18 @@
+<?PHP
+declare(strict_types = 1);
+
+/**
+ * Exception thrown in case a user attempts to generate timeline page when it should not be available.
+ */
+final class MDTimelineNotAvailable extends Exception {
+    /**
+     * Error message.
+     *
+     * @return string
+     */
+    public function errorMessage() {
+        //error message
+        return 'Timeline cannot be generated for this query.';
+
+    }
+}