title: .toPromise().then(...).catch(...).finally is not a function
body: <p>I'm getting this error on Firefox and I'm using rxjs 6.5.4 version:</p>
  <blockquote>
  <p>Unhandled promise rejection TypeError:
  this.service.getPastData2(...).toPromise().then(...).catch(...).finally
  is not a function</p>
  </blockquote>
  <p>My code:</p>
  <pre><code>lineMap(criteria: ReportCriterionModel){
  
          this.service
              .getPastData2(
                  criteria.deviceIds[0].toString(),
                  criteria.vehiclePlates[0].toString(),
                  criteria.startDate,
                  criteria.finishDate)      
              .toPromise()
              .then(
                  (data) =&gt; {   
                      this.loadDataToMap(data);  
                      this.filterData = criteria;      
                  },
                  (err) =&gt; {
                      if (err.status == 400) {                    
                          this.isLoadingFms.next(false);
                      }                    
                  }
              )
              .catch(
                  (err) =&gt; {
                      console.log(err);
                  }
              )
              .finally(
                  () =&gt; {                                              
                      this.isLoadingFms.next(false);
                      
                  }
              )
  
      }
  </code></pre>