fix: don't fail when posix env var is not present (#1018)

* fix: don't set MacOS specific values when not on MacOS

* refactor: use dict.get instead

src/tagstudio/qt/helpers/vendored/ffmpeg.py

@@ -16,7 +16,7 @@ from tagstudio.qt.helpers.silent_popen import silent_Popen, silent_run
 
 logger = structlog.get_logger(__name__)
 
-user = os.environ["USER"]
+user = os.environ.get("USER", None)
 FFMPEG_MACOS_LOCATIONS: list[str] = [
     "",
     "/opt/homebrew/bin/",
@@ -65,7 +65,7 @@ def probe(filename, cmd=FFPROBE_CMD, timeout=None, **kwargs):
             ``stderr`` property of the exception.
     """
     args = [cmd, "-show_format", "-show_streams", "-of", "json"]
-    args += ffmpeg._utils.convert_kwargs_to_cmd_line_args(kwargs)
+    args += ffmpeg._utils.convert_kwargs_to_cmd_line_args(kwargs)  # pyright: ignore[reportAttributeAccessIssue]
     args += [filename]
 
     # PATCHED