avoid minor redundancy in generated code

Cython/Compiler/Nodes.py

@@ -2021,6 +2021,7 @@ class DefNode(FuncDefNode):
         elif min_positional_args == max_positional_args:
             # parse the exact number of positional arguments from the
             # args tuple
+            if max_positional_args > 0:
                 code.putln('} else {')
                 for i, arg in enumerate(positional_args):
                     item = "PyTuple_GET_ITEM(%s, %d)" % (Naming.args_cname, i)