[db] fix passing inverse format list

1 files changed, 3 insertions, 2 deletions

diff --git a/src/luaotfload-database.lua b/src/luaotfload-database.lua
index b871954..086f46f 100644
--- a/src/luaotfload-database.lua
+++ b/src/luaotfload-database.lua
@@ -1921,9 +1921,8 @@ end
 local p_font_filter
 
 do
-    local current_formats = { }
-
     local extension_pattern = function (list)
+        if type (list) ~= "table" or #list == 0 then return P(-1) end
         local pat
         for i=#list, 1, -1 do
             local e = list[i]
@@ -1940,6 +1939,8 @@ do
     --- small helper to adjust the font filter pattern (--formats
     --- option)
 
+    local current_formats = { }
+
     set_font_filter = function (formats)
 
         if not formats or type (formats) ~= "string" then