Fix mypy type errors

src/photomanager/cli.py

@@ -113,7 +113,7 @@ def _create(
 @click.argument("paths", nargs=-1, type=click.Path())
 # fmt: on
 def _index(
-    db: Union[str, PathLike] = None,
+    db: Optional[Union[str, PathLike]] = None,
     source: Optional[Union[str, PathLike]] = None,
     file: Optional[Union[str, PathLike]] = None,
     paths: Iterable[Union[str, PathLike]] = tuple(),

src/photomanager/photofile.py

@@ -165,7 +165,10 @@ def to_dict(self) -> dict:
         return asdict(self)
 
 
-def datetime_str_to_object(ts_str: str, tz_default: tzinfo = None) -> datetime:
+def datetime_str_to_object(
+    ts_str: str,
+    tz_default: Optional[tzinfo] = None,
+) -> datetime:
     """Parses a datetime string into a datetime object"""
     dt = None
     if "." in ts_str:
@@ -186,7 +189,7 @@ def datetime_str_to_object(ts_str: str, tz_default: tzinfo = None) -> datetime:
             except ValueError:
                 pass  # failed parsing is handled below
     if dt is not None:
-        if dt.tzinfo is None:
+        if dt.tzinfo is None and tz_default is not None:
             dt = dt.replace(tzinfo=tz_default)
         return dt
     raise ValueError(f"Could not parse datetime str: {repr(ts_str)}")

src/photomanager/pyexiftool/pyexiftool_async.py

@@ -112,15 +112,15 @@ def make_chunk_jobs(
 class AsyncExifTool(AsyncWorkerQueue):
     def __init__(
         self,
-        executable_: str = None,
+        executable_: str = "",
         num_workers: int = os.cpu_count() or 1,
         show_progress: bool = True,
         batch_size: int = 20,
     ):
         super(AsyncExifTool, self).__init__(
             num_workers=num_workers, show_progress=show_progress
         )
-        self.executable = executable if executable_ is None else executable_
+        self.executable = executable if not executable_ else executable_
         self.running = False
         self.queue = None
         self.batch_size = batch_size