Add null checks to config setters

Author: RovinKYK

components/org.wso2.carbon.identity.api.server.common/src/main/java/org/wso2/carbon/identity/api/server/common/file/FileSerializationConfig.java

@@ -83,6 +83,9 @@ public DefaultFormat getSerializeDefault() {
 
     public void setSerializeDefault(DefaultFormat serializeDefault) {
 
+        if (serializeDefault == null) {
+            throw new IllegalArgumentException("serializeDefault cannot be null");
+        }
         this.serializeDefault = serializeDefault;
     }
 
@@ -92,6 +95,9 @@ public DefaultFormat getDeserializeDefault() {
 
     public void setDeserializeDefault(DefaultFormat deserializeDefault) {
 
+        if (deserializeDefault == null) {
+            throw new IllegalArgumentException("deserializeDefault cannot be null");
+        }
         this.deserializeDefault = deserializeDefault;
     }
 }

components/org.wso2.carbon.identity.api.server.common/src/main/java/org/wso2/carbon/identity/api/server/common/file/YamlConfig.java

@@ -84,6 +84,9 @@ public List<String> getAdditionalTrustedClassNames() {
     public void setAdditionalTrustedClasses(Class<?>... classes) {
 
         this.additionalTrustedClassNames = new ArrayList<>();
+        if (classes == null) {
+            return;
+        }
         for (Class<?> clazz : classes) {
             this.additionalTrustedClassNames.add(clazz.getName());
         }