fix size bug in _mesa_add_attribute()
diff --git a/src/mesa/shader/prog_parameter.c b/src/mesa/shader/prog_parameter.c
index fbc3839..676f172 100644
--- a/src/mesa/shader/prog_parameter.c
+++ b/src/mesa/shader/prog_parameter.c
@@ -297,6 +297,8 @@
       /* add */
       gl_state_index state[STATE_LENGTH];
       state[0] = attrib;
+      if (size < 0)
+         size = 4;
       i = _mesa_add_parameter(paramList, PROGRAM_INPUT, name,
                               size, NULL, state);
    }