Created by: luotao1

mutable _data的错误，就是如果shape设置错了，mutable data的时候就会报错，说numel=-1，但是没有把具体的shape给出来 @phlrain 提出

这个PR会把shape打出。类似以下截图

文字版类似：

30: C++ exception with description "Enforce failed. Expected numel() <= 0, but received numel():216 > 0:0.
30: When calling this method, the Tensor's numel must be equal or larger than zero. Please check Tensor::Resize has been called first. The Tensor's shape is [2, 3, 4, 9] now at [/home/luotao/Paddle/paddle/fluid/framework/tensor.cc:44]