ui: Replace ErrorMessages getter with indexing operator

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

ui/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.kt

@@ -34,7 +34,7 @@ class ModuleDownloaderPreference(context: Context, attrs: AttributeSet?) : Prefe
         when {
             throwable != null -> {
                 setState(State.FAILURE)
-                Toast.makeText(context, ErrorMessages.get(throwable), Toast.LENGTH_LONG).show()
+                Toast.makeText(context, ErrorMessages[throwable], Toast.LENGTH_LONG).show()
             }
             result == OsConstants.ENOENT -> setState(State.NOTFOUND)
             result == OsConstants.EXIT_SUCCESS -> {

ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.kt

@@ -63,7 +63,7 @@ class ZipExporterPreference(context: Context, attrs: AttributeSet?) : Preference
 
     private fun exportZipComplete(filePath: String?, throwable: Throwable?) {
         if (throwable != null) {
-            val error = ErrorMessages.get(throwable)
+            val error = ErrorMessages[throwable]
             val message = context.getString(R.string.zip_export_error, error)
             Log.e(TAG, message, throwable)
             Snackbar.make(