fixed functionblock ast serialization to recursively perform empty ar…

…gs sanity check for nested function calls

tinycss2/ast.py

@@ -694,15 +694,14 @@ def _serialize_to(self, write):
         write(serialize_identifier(self.name))
         write('(')
         _serialize_to(self.arguments, write)
-        if self.arguments:
-            function = self
-            while isinstance(function, FunctionBlock):
-                eof_in_string = (
-                    isinstance(function.arguments[-1], ParseError) and
-                    function.arguments[-1].kind == 'eof-in-string')
-                if eof_in_string:
-                    return
-                function = function.arguments[-1]
+        function = self
+        while isinstance(function, FunctionBlock) and function.arguments:
+            eof_in_string = (
+                isinstance(function.arguments[-1], ParseError) and
+                function.arguments[-1].kind == 'eof-in-string')
+            if eof_in_string:
+                return
+            function = function.arguments[-1]
         write(')')