Connector reassigns read-only properties of errors

[sharafian]

ilp-connector/src/services/middleware-manager.ts

Lines 157 to 169 in 5292ad4

	let err = e
	if (!err || typeof err !== 'object') {
	err = new Error('non-object thrown. value=' + e)
	}
	if (!err.ilpErrorCode) {
	err.ilpErrorCode = codes.F02_UNREACHABLE
	}
	err.message = 'failed to send packet: ' + err.message
	throw err
	}

This code sets the .ilpErrorCode and .message fields of an error thrown from a plugin's sendData. What we're seeing is that this can trigger a new error:

2018-07-12T17:15:49.225Z ilp-protocol-stream:Client:Connection:debug debug test packet 2 was rejected with a F00 error with the message: "Cannot assign to read only property 'message' of object 'UnreachableError: account must be in READY state to receive packets. state=BLOCKED'"

Instead, this catch block should just construct a new error