Index: src/bp-templates/bp-legacy/buddypress-functions.php
===================================================================
--- src/bp-templates/bp-legacy/buddypress-functions.php
+++ src/bp-templates/bp-legacy/buddypress-functions.php
@@ -497,6 +497,14 @@
 		// Add it to the beginning of the templates array so it takes precedence
 		// over the default hierarchy.
 		if ( ! empty( $page_template ) ) {
+			// Get all valid custom page templates
+			$theme_custom_templates = wp_get_theme()->get_page_templates( $page_id );
+
+			// Check existence of custom page template; if doesn't exist, bail.
+			if ( ! isset( $page_templates[ $page_template ] ) ) {
+				return $templates;
+			}
+
 			array_unshift( $templates, $page_template );
 		}