Do not attempt to del transport in connection_lost if it has been alr…

…eady (#215)

edgedb/protocol/asyncio_proto.pyx

@@ -112,13 +112,14 @@ cdef class AsyncIOProtocol(protocol.SansIOProtocol):
             self.msg_waiter.set_exception(ConnectionResetError())
             self.msg_waiter = None
 
-        # With asyncio sslproto on CPython 3.10 or lower, a normal exit
-        # (connection closed by peer) cannot set the transport._closed
-        # properly, leading to false ResourceWarning. Let's fix that by
-        # closing the transport again.
-        if not self.transport.is_closing():
-            self.transport.close()
-        self.transport = None
+        if self.transport is not None:
+            # With asyncio sslproto on CPython 3.10 or lower, a normal exit
+            # (connection closed by peer) cannot set the transport._closed
+            # properly, leading to false ResourceWarning. Let's fix that by
+            # closing the transport again.
+            if not self.transport.is_closing():
+                self.transport.close()
+            self.transport = None
 
     def pause_writing(self):
         pass