Check whether input type is missing for function shape inference

[jcwchen]

Description
To fix crash, check whether input type is missing for function shape inference

Motivation and Context
Shape inference for function assumes input type will be always exist:

onnx/onnx/shape_inference/implementation.cc

Line 642 in c7a9e9c

types_cache[i] = *ctx.getInputType(i);

. However, if input type is missing, shape inference will crash. It should first examine whether input type exists. Ideally every type should be provided in ONNX, but if there are some custom operators before this function node, it is possible that such a type is missing without defined opset schema. At least shape inference should not crash with this case.

cc @yufenglee