Make IQ.type private

to prevent subclasses form setting type to null.

smack-core/src/main/java/org/jivesoftware/smack/packet/EmptyResultIQ.java

@@ -20,7 +20,7 @@ public class EmptyResultIQ extends IQ {
 
     public EmptyResultIQ() {
         super(null, null);
-        type = IQ.Type.result;
+        setType(IQ.Type.result);
     }
 
     public EmptyResultIQ(IQ request) {

smack-core/src/main/java/org/jivesoftware/smack/packet/ErrorIQ.java

@@ -32,7 +32,7 @@ public class ErrorIQ extends SimpleIQ {
         if (xmppError == null) {
             throw new IllegalArgumentException("XMPPError must not be null");
         }
-        type = IQ.Type.error;
+        setType(IQ.Type.error);
         setError(xmppError);
     }
 

smack-core/src/main/java/org/jivesoftware/smack/packet/IQ.java

@@ -47,7 +47,7 @@ public abstract class IQ extends Packet {
     private final String childElementName;
     private final String childElementNamespace;
 
-    protected Type type = Type.get;
+    private Type type = Type.get;
 
     public IQ(IQ iq) {
         super(iq);

smack-experimental/src/main/java/org/jivesoftware/smackx/hoxt/packet/HttpOverXmppReq.java

@@ -33,7 +33,7 @@ public class HttpOverXmppReq extends AbstractHttpOverXmpp {
         super(ELEMENT);
         this.method = method;
         this.resource = resource;
-        type = Type.set;
+        setType(Type.set);
     }
 
     private HttpMethod method;