Avoid NPE when a connect address isn't specified and newHandler is in use

[violetagg]

In case of HttpClient used with a specified request type and no connect address,
it will be calculated based on the url (HttpClientOptions#formatSchemeAndHost).
In case no request type is specified, but newHandler is used, the HttpClient will try
to connect to https://localhost.

java.lang.NullPointerException
	at reactor.ipc.netty.resources.DefaultPoolResources$SocketAddressHolder.hashCode(DefaultPoolResources.java:294)
	at java.util.concurrent.ConcurrentHashMap.get(ConcurrentHashMap.java:936)
	at reactor.ipc.netty.resources.DefaultPoolResources.selectOrCreate(DefaultPoolResources.java:73)
	at reactor.ipc.netty.tcp.TcpResources.selectOrCreate(TcpResources.java:157)
	at reactor.ipc.netty.tcp.TcpClient.lambda$newHandler$1(TcpClient.java:181)
	at reactor.core.publisher.MonoCreate.subscribe(MonoCreate.java:53)
	at reactor.core.publisher.Mono.block(Mono.java:1498)

[codecov-io]

Codecov Report

Merging #474 into 0.7.x will increase coverage by 0.15%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##              0.7.x   #474      +/-   ##
==========================================
+ Coverage     67.84%    68%   +0.15%     
- Complexity     1074   1080       +6     
==========================================
  Files            73     73              
  Lines          4615   4622       +7     
  Branches        661    662       +1     
==========================================
+ Hits           3131   3143      +12     
+ Misses         1096   1089       -7     
- Partials        388    390       +2

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/reactor/ipc/netty/tcp/TcpClient.java	90.56% <ø> (ø)	20 <0> (ø)	⬇️
...actor/ipc/netty/http/client/HttpClientOptions.java	86.44% <100%> (+0.47%)	24 <0> (+1)	⬆️
...java/reactor/ipc/netty/http/client/HttpClient.java	73.97% <33.33%> (-2.5%)	26 <1> (+1)
.../ipc/netty/http/server/HttpServerWSOperations.java	60% <0%> (+1.42%)	17% <0%> (+1%)	⬆️
.../ipc/netty/channel/PooledClientContextHandler.java	71.42% <0%> (+5.04%)	28% <0%> (+2%)	⬆️
...va/reactor/ipc/netty/channel/AbortedException.java	43.75% <0%> (+6.25%)	6% <0%> (+1%)	⬆️

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