fix guide.getParams

Author: fesily

script/parser/guide.lua

@@ -1313,12 +1313,18 @@ end
 function m.getParams(source)
     if source.type == 'call' then
         local args = source.args
+        if not args then
+            return
+        end
         assert(args.type == 'callargs', 'call.args type is\'t callargs')
         return args
     elseif source.type == 'callargs' then
         return source
     elseif source.type == 'function' then
         local args = source.args
+        if not args then
+            return
+        end
         assert(args.type == 'funcargs', 'function.args type is\'t callargs')
         return args
     end