Use explicit type cast for Collection.emptyMap

Author: puneetbehl

grails-datastore-gorm-rx/src/main/groovy/grails/gorm/rx/RxEntity.groovy

@@ -504,7 +504,7 @@ trait RxEntity<D> implements RxGormOperations<D>, GormValidateable, DirtyCheckab
      * @return An observable with all results
      */
     static Observable<D> findAll() {
-        findAll(Collections.emptyMap())
+        findAll(Collections.<String, Object> emptyMap())
     }
 
     /**
@@ -707,4 +707,4 @@ trait RxEntity<D> implements RxGormOperations<D>, GormValidateable, DirtyCheckab
     private static RxGormStaticApi<D> currentRxGormStaticApi() {
         (RxGormStaticApi<D>)RxGormEnhancer.findStaticApi(this)
     }
-}
+}