fix(config): prevent FileObserver NPE on config file deletion

When a config file is deleted, the event handler sets file=null but
then force-unwraps it with file!! in the when block, crashing the
FileObserver thread. All subsequent config change notifications are
silently lost.

Replace force-unwrap with safe call, log a warning on deletion.

app/src/main/java/org/matrix/TEESimulator/config/ConfigurationManager.kt

@@ -307,8 +307,10 @@ object ConfigurationManager {
 
             val file = if (event != DELETE) File(configRoot, path) else null
             when (path) {
-                TARGET_PACKAGES_FILE -> loadTargetPackages(file!!)
-                PATCH_LEVEL_FILE -> loadPatchLevelConfig(file!!)
+                TARGET_PACKAGES_FILE -> file?.let { loadTargetPackages(it) }
+                    ?: SystemLogger.warning("$TARGET_PACKAGES_FILE was deleted.")
+                PATCH_LEVEL_FILE -> file?.let { loadPatchLevelConfig(it) }
+                    ?: SystemLogger.warning("$PATCH_LEVEL_FILE was deleted.")
                 // Any change to an XML file is assumed to be a keybox.
                 // The cache in KeyBoxManager will handle reloading it on its next use.
                 else ->