bpo-41149: Fix a bug in threading that causes fals-y threads callables to fail to start. (GH-21201)

diff --git a/Lib/threading.py b/Lib/threading.py
index 7b3d63d..ff2624a 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -906,7 +906,7 @@ def run(self):
 
         """
         try:
-            if self._target:
+            if self._target is not None:
                 self._target(*self._args, **self._kwargs)
         finally:
             # Avoid a refcycle if the thread is running a function with