Index: bp-core/bp-core-avatars.php
===================================================================
--- bp-core/bp-core-avatars.php	(revision 11636)
+++ bp-core/bp-core-avatars.php	(working copy)
@@ -1383,8 +1383,10 @@
 	} elseif ( $id_or_email instanceof WP_Post ) {
 		// Post Object
 		$user = get_user_by( 'id', (int) $id_or_email->post_author );
-	} elseif ( $id_or_email instanceof WP_Comment && ! empty( $id_or_email->user_id ) ) {
-		$user = get_user_by( 'id', (int) $id_or_email->user_id );
+	} elseif ( $id_or_email instanceof WP_Comment ) {
+		if ( ! empty( $id_or_email->user_id ) ) {
+			$user = get_user_by( 'id', (int) $id_or_email->user_id );
+		}
 	} elseif ( is_email( $id_or_email ) ) {
 		$user = get_user_by( 'email', $id_or_email );
 	}