Fix a few possible null dereferences by adding additional checks

Author: stevenlagoy

src/main/java/core/FileOperations.java

@@ -93,8 +93,9 @@ public static Set<Path> listFiles(Path dir, FileExtension extension) throws IOEx
                 if (path == null || path.getFileName() == null) {
                     continue; // Skip null paths
                 }
-                String fileName = path.getFileName().toString();
-                if (!Files.isDirectory(path) && !FilePaths.IGNORED_FILES.contains(fileName)
+                Path fileName = path.getFileName();
+                if (fileName == null) return null;
+                if (!Files.isDirectory(path) && !FilePaths.IGNORED_FILES.contains(fileName.toString())
                         && fileName.endsWith(extension.getExtension())) {
                     pathSet.add(dir.resolve(fileName));
                 }

src/main/java/core/JSONProcessor.java

@@ -39,7 +39,9 @@ public class JSONProcessor {
     public static JSONObject processJson(Path path) {
         if (path == null) return null;
         List<String> contents = FileOperations.readFile(path);
-        String key = path.getFileName().toString().split("\\.")[0];
+        Path fileName = path.getFileName();
+        if (fileName == null) return null;
+        String key = fileName.toString().split("\\.")[0];
         return processJson(key, contents);
     }