[BUGFIX] happy eye: null pointer on closed socket if no connection was etablished

src/main/java/eu/siacs/conversations/utils/Resolver.java

@@ -428,7 +428,10 @@ public class Resolver {
         @Override
         public Result call() throws Exception {
             this.connect();
-            return this.socket.isConnected() ? this : null;
+            if (this.socket != null && this.socket.isConnected()) {
+	        return this ;
+            }
+            return null;
         }
 
         public ContentValues toContentValues() {