Check getTlsTrustStorePath NPE when user forget to set it. (apach…

…e#14253)

If a user sets ``useKeyStoreTls=true`` then forget to set ``getTlsTrustStorePath``, we’re having NPE which becomes hard to debug for users.

- Add NPE check and give use more clear error information.

- [x] Make sure that the change passes the CI checks.

*If `yes` was chosen, please highlight the changes*

  - Dependencies (does it add or upgrade a dependency): (no)
  - The public API: (no)
  - The schema: (no)
  - The default values of configurations: (no)
  - The wire protocol: (no)
  - The rest endpoints: (no)
  - The admin cli options: (no)
  - Anything that affects deployment: (no)

- [x] `no-need-doc`

(cherry picked from commit eca563e)

pulsar-client/src/main/java/org/apache/pulsar/client/impl/PulsarChannelInitializer.java

@@ -23,8 +23,11 @@
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Supplier;
-
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.commons.lang3.StringUtils;
 import org.apache.pulsar.client.api.AuthenticationDataProvider;
+import org.apache.pulsar.client.api.PulsarClientException;
 import org.apache.pulsar.client.impl.conf.ClientConfigurationData;
 import org.apache.pulsar.client.util.ObjectCache;
 import org.apache.pulsar.common.protocol.ByteBufPair;
@@ -38,8 +41,6 @@
 import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
 import io.netty.handler.ssl.SslContext;
 import io.netty.handler.ssl.SslHandler;
-import lombok.Getter;
-import lombok.extern.slf4j.Slf4j;
 
 @Slf4j
 public class PulsarChannelInitializer extends ChannelInitializer<SocketChannel> {
@@ -66,7 +67,10 @@ public PulsarChannelInitializer(ClientConfigurationData conf, Supplier<ClientCnx
         if (tlsEnabled) {
             if (tlsEnabledWithKeyStore) {
                 AuthenticationDataProvider authData1 = conf.getAuthentication().getAuthData();
-
+                if (StringUtils.isBlank(conf.getTlsTrustStorePath())) {
+                    throw new PulsarClientException("Failed to create TLS context, the tlsTrustStorePath"
+                            + " need to be configured if useKeyStoreTls enabled");
+                }
                 nettySSLContextAutoRefreshBuilder = new NettySSLContextAutoRefreshBuilder(
                             conf.getSslProvider(),
                             conf.isTlsAllowInsecureConnection(),