[Minor] Fix issues with values check

lualib/lua_mime.lua

@@ -526,8 +526,10 @@ exports.modify_headers = function(task, hdr_alterations)
     local add_tbl = hdr_flattened[hname].add
     if hdr.value then
       table.insert(add_tbl, {hdr.order or -1, hdr.value})
-    else
-      table.insert(add_tbl, {-1, hdr})
+    elseif type(hdr) == 'table' then
+      for _,v in ipairs(hdr) do
+        table.insert(add_tbl, {-1, v})
+      end
     end
   end
 

src/libmime/mime_headers.c

@@ -1894,7 +1894,9 @@ rspamd_message_set_modified_header (struct rspamd_task *task,
 				const ucl_object_t *order = ucl_array_find_index (cur, 0),
 					*value = ucl_array_find_index (cur, 1);
 
-				if (order && value) {
+				if (order && value &&
+					(ucl_object_type (order) == UCL_INT &&
+					 ucl_object_type (value) == UCL_STRING)) {
 					int ord = ucl_object_toint (order);
 					const char *raw_value;
 					gsize raw_len;