fix: resolve CI linting and type checking issues

config_converter/converters/json_converter.py

@@ -2,7 +2,7 @@
 
 import json
 from pathlib import Path
-from typing import Any, Dict
+from typing import Any, Dict, Union
 
 from config_converter.converters.base import BaseConverter, ConversionError
 
@@ -13,11 +13,12 @@ class JsonConverter(BaseConverter):
     FORMAT_NAME = "json"
     FILE_EXTENSIONS = ["json"]
 
-    def read(self, source: str | Path) -> Dict[str, Any]:
+    def read(self, source: Union[str, Path]) -> Dict[str, Any]:
         """Read and parse a JSON configuration file."""
         try:
             with open(source, "r", encoding="utf-8") as f:
-                return json.load(f)
+                data = json.load(f)
+                return data if data is not None else {}
         except json.JSONDecodeError as e:
             raise ConversionError(f"Invalid JSON in {source}: {e}") from e
         except FileNotFoundError as e:
@@ -25,7 +26,7 @@ class JsonConverter(BaseConverter):
         except PermissionError as e:
             raise ConversionError(f"Permission denied: {source}") from e
 
-    def write(self, data: Dict[str, Any], target: str | Path) -> None:
+    def write(self, data: Dict[str, Any], target: Union[str, Path]) -> None:
         """Write configuration data to a JSON file."""
         try:
             with open(target, "w", encoding="utf-8") as f:
@@ -36,7 +37,8 @@ class JsonConverter(BaseConverter):
     def parse(self, content: str) -> Dict[str, Any]:
         """Parse JSON content from a string."""
         try:
-            return json.loads(content)
+            data = json.loads(content)
+            return data if data is not None else {}
         except json.JSONDecodeError as e:
             raise ConversionError(f"Invalid JSON content: {e}") from e