TimerHandle.when() segfault fix

tests/test_uv_timer_when_after_cb.py

@@ -0,0 +1,13 @@
+import uvloop
+import asyncio
+
+
+async def main():
+    loop = asyncio.get_running_loop()
+    call_ts = loop.time() + 1
+    timer = loop.call_at(call_ts, lambda: None) # call any function
+    await asyncio.sleep(1.1)
+    assert timer.when() == call_ts
+
+uvloop.install()
+asyncio.run(main(), debug=True)

uvloop/cbhandles.pyx

@@ -215,7 +215,7 @@ cdef class TimerHandle:
         self._clear()
 
     cdef inline _clear(self):
-        if self.timer is None:
+        if self not in self.loop._timers: # check if timer has already been removed
             return
 
         self.callback = None
@@ -225,7 +225,7 @@ cdef class TimerHandle:
             self.loop._timers.remove(self)
         finally:
             self.timer._close()
-            self.timer = None  # let the UVTimer handle GC
+            # self.timer = None  # let the UVTimer handle GC this will cause a segfault if .when() is called beyond this point
 
     cdef _run(self):
         if self._cancelled == 1: