title: Retrofit Observable Call() method Not set baseUrl and throw NP Exception
body: <p>When call() method compile it doesn't set Endpoint url and throw NP Exception</p>
  
  <pre><code>        public Observable&lt;ResultPojo&gt; call() {
              final ResultPojo resultPojo;
  
              try {
                  resultPojo = buildRestAdapter().registerSubDistributor
                          (subDistributorDetailModel.getRoleType(),
                                  subDistributorDetailModel.getPassword(),
                                  subDistributorDetailModel.getUserName(),
                                  subDistributorDetailModel.getMobileNumber(),
                                  subDistributorDetailModel.getAddress(),
                                  subDistributorDetailModel.getFirmName(),
                                  subDistributorDetailModel.getAge(),
                                  subDistributorDetailModel.getFathersName());
              } catch (Exception e) {
                  throw OnErrorThrowable.from(e);
              }
              return Observable.just(resultPojo);
          }
      });
  }
  </code></pre>
  
  <p>"Method for Build RestAdapter and it Return apiManager Object"</p>
  
  <pre><code>private static SubDistributorApiManager buildRestAdapter(){
  
      Builder builder = new Builder()
              .setEndpoint(SubDistributorApiManager.BASE_URL);
  
      RestAdapter restAdapter = builder.build();
      SubDistributorApiManager apiManager = restAdapter.create(SubDistributorApiManager.class);
  
  
      return apiManager;
  }
  </code></pre>