Return empty array or 0 in Database methods when first param is null

main/inc/lib/database.lib.php

@@ -269,6 +269,10 @@ class Database
      */
     public static function fetch_assoc(Statement $result)
     {
+        if ($result === false) {
+            return array();
+        }
+
         return $result->fetch(PDO::FETCH_ASSOC);
     }
 
@@ -295,6 +299,9 @@ class Database
      */
     public static function fetch_row(Statement $result)
     {
+        if ($result === false) {
+            return array();
+        }
         return $result->fetch(PDO::FETCH_NUM);
     }
 
@@ -326,6 +333,9 @@ class Database
      */
     public static function num_rows(Statement $result)
     {
+        if ($result === false) {
+            return 0;
+        }
         return $result->rowCount();
     }