[FABJ-377] Possible NPE in SDKUtils

There is a null reference check for "client" in SDKUtils.calculateBlockHash()
It should be on "cryptoSuite" instead of "client"

- check "cryptoSuite" instead of "client" for null reference

Change-Id: I67bad22ba19d08130b43fb0a346e1577204962aa
Signed-off-by: Ivo Huisjes <fabric-sdk@spam4.me>

src/main/java/org/hyperledger/fabric/sdk/SDKUtils.java

@@ -62,7 +62,7 @@ public static byte[] calculateBlockHash(HFClient client, long blockNumber, byte[
         }
 
         CryptoSuite cryptoSuite = client.getCryptoSuite();
-        if (null == client) {
+        if (null == cryptoSuite) {
             throw new InvalidArgumentException("Client crypto suite has not  been set.");
         }