Close the param threads properly if close is called.

Put a None object on the queue if closed and read this out.
The lock was released but since the queue was emptied the run task would never return
from queue.get() and then this thread could not be closed. Make sure to
unblock it by sending None and then setting should_close variable

Author: ToveRumar

cflib/crazyflie/param.py

@@ -576,6 +576,8 @@ def _close(self):
 
         # Then force an unlock of the mutex if we are waiting for a packet
         # we didn't get back due to a disconnect for example.
+        self._should_close = True
+        self.request_queue.put(None)
         try:
             self._lock.release()
         except RuntimeError:
@@ -584,6 +586,8 @@ def _close(self):
     def run(self):
         while not self._should_close:
             pk = self.request_queue.get()  # Wait for request update
+            if pk is None:  # Put none to close the thread
+                continue
             self._lock.acquire()
             if self._cf.link:
                 self._req_param = struct.unpack('<H', pk.data[1:3])[0]
@@ -616,9 +620,11 @@ def close(self):
                 self.request_queue.get(block=False)
         except Empty:
             pass
-
+        self._should_close = True
+        self.request_queue.put(None)
         # Then force an unlock of the mutex if we are waiting for a packet
         # we didn't get back due to a disconnect for example.
+
         try:
             self.wait_lock.release()
         except RuntimeError:
@@ -677,6 +683,8 @@ def request_param_update(self, var_id):
     def run(self):
         while not self._should_close:
             pk = self.request_queue.get()  # Wait for request update
+            if pk is None:  # Put none to close the thread
+                continue
             self.wait_lock.acquire()
             if self.cf.link:
                 if self._useV2: