Fix busted test

Author: DylanRussell

opentelemetry-sdk/src/opentelemetry/sdk/_logs/_internal/__init__.py

@@ -237,7 +237,7 @@ def to_json(self, indent: int | None = 4) -> str:
                 ),
                 "dropped_attributes": self.dropped_attributes,
                 "timestamp": ns_to_iso_str(self.timestamp)
-                if self.timestamp
+                if self.timestamp is not None
                 else None,
                 "observed_timestamp": ns_to_iso_str(self.observed_timestamp),
                 "trace_id": (