For .active property, check for .closed first

This way, a closed stream can be active==False instead of throwing an
exception.

Author: mgeier

sounddevice.py

@@ -1162,6 +1162,8 @@ def active(self):
         stopped
 
         """
+        if self.closed:
+            return False
         return _check(_lib.Pa_IsStreamActive(self._ptr)) == 1
 
     @property