chore: fix tests

stream can return `None`

tests/test_sanity.py

@@ -10,9 +10,11 @@ def test_sanity():
 
 def test_run_simple():
     for line in bitia.__main__.run_pipeline("ls -ltr /"):
-        print(111, line.decode().rstrip())
+        if line:
+            print(111, line.decode().rstrip())
     for line in bitia.__main__.run_pipeline("ls -ltr /", rerun=True):
-        print(222, line.decode().rstrip())
+        if line:
+            print(222, line.decode().rstrip())
 
 
 if __name__ == "__main__":