Caught exception and added rst warning for when struct/class not found
Caught exception and added rst warning for when struct/class not found

If a struct/class name was not found in a project the exception thrown
would halt Sphinx. Now it is caught and a warning rst node is output to
indicate the failure.

AnthonyTruchet/breathe,kirbyfan64/breathe,kirbyfan64/breathe,AnthonyTruchet/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,RR2DO2/breathe,AnthonyTruchet/breathe,RR2DO2/breathe,kirbyfan64/breathe