update null value checking and empty string

Author: kelvinwijaya

src/main/java/com/api/util/ApiSecurity/ApiList.java

@@ -43,7 +43,7 @@ public String toString(String delimiter, Boolean sort, Boolean quote, Boolean is
 						return l1.getKey().equals(l2.getKey()) ? l1.getValue().compareTo(l2.getValue())
 									: l1.getKey().compareTo(l2.getKey());
 					})
-					.map(e -> (e.getValue()=="" && isBaseString) ? e.getKey() : String.format(format, e.getKey(), e.getValue())  )
+					.map(e -> (null!= e.getValue() && e.getValue().equals("") && isBaseString) ? e.getKey() : String.format(format, e.getKey(), e.getValue())  )
 					.collect(Collectors.toList());
 		} else{
 			list = this.stream().map(e -> String.format(format, e.getKey(), e.getValue()))

src/main/java/com/api/util/ApiSecurity/ApiSigning.java

@@ -501,7 +501,7 @@ public static String getSignatureToken(
 
             // Generate the nonce value
             try {
-                nonce = nonce != null ? nonce : getNewNonce();
+                nonce = (nonce != null && !nonce.isEmpty())  ? nonce : getNewNonce();
             } catch (NoSuchAlgorithmException nsae) {
                 throw nsae;
             }