Fix asserts in Array.cs

[stephentoub]

Fixes#35438
cc: @jkotas

[jkotas]

dotnet-runtime-perf failure is infrastructure issue #33082

2020-04-25T12:09:35.1543465Z [2020/04/25 12:09:35][INFO] Downloading https://dot.net/v1/dotnet-install.ps1
2020-04-25T12:09:36.4769149Z Traceback (most recent call last):
2020-04-25T12:09:36.4770530Z File "C:\python3.7.0\lib\urllib\request.py", line 1317, in do_open
2020-04-25T12:09:36.4771251Z encode_chunked=req.has_header('Transfer-encoding'))
2020-04-25T12:09:36.4771840Z File "C:\python3.7.0\lib\http\client.py", line 1229, in request
2020-04-25T12:09:36.4772421Z self._send_request(method, url, body, headers, encode_chunked)
2020-04-25T12:09:36.4773014Z File "C:\python3.7.0\lib\http\client.py", line 1275, in _send_request
2020-04-25T12:09:36.4773542Z self.endheaders(body, encode_chunked=encode_chunked)
2020-04-25T12:09:36.4774197Z File "C:\python3.7.0\lib\http\client.py", line 1224, in endheaders
2020-04-25T12:09:36.4774797Z self._send_output(message_body, encode_chunked=encode_chunked)
2020-04-25T12:09:36.4775250Z File "C:\python3.7.0\lib\http\client.py", line 1016, in _send_output
2020-04-25T12:09:36.4775692Z self.send(msg)
2020-04-25T12:09:36.4776102Z File "C:\python3.7.0\lib\http\client.py", line 956, in send
2020-04-25T12:09:36.4776487Z self.connect()
2020-04-25T12:09:36.4776893Z File "C:\python3.7.0\lib\http\client.py", line 1392, in connect
2020-04-25T12:09:36.4777720Z server_hostname=server_hostname)
2020-04-25T12:09:36.4778179Z File "C:\python3.7.0\lib\ssl.py", line 412, in wrap_socket
2020-04-25T12:09:36.4778630Z session=session
2020-04-25T12:09:36.4779059Z File "C:\python3.7.0\lib\ssl.py", line 850, in _create
2020-04-25T12:09:36.4779501Z self.do_handshake()
2020-04-25T12:09:36.4779961Z File "C:\python3.7.0\lib\ssl.py", line 1108, in do_handshake
2020-04-25T12:09:36.4780398Z self._sslobj.do_handshake()
2020-04-25T12:09:36.4782191Z ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host