[fix] open the FlutterModuleBuilder error dialog on the EDT (#8259)

`FlutterModuleBuilder` settings validation happens off the `EDT`, which
is great for performance but it means we need to take an extra step when
wanting to display dialogs.

Fixes: #8243

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portions to this PR.

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Author: pq

flutter-idea/src/io/flutter/module/FlutterModuleBuilder.java

@@ -258,7 +258,9 @@ private static VirtualFile findEmbeddedModuleFile(@NotNull VirtualFile baseDir,
   public boolean validate(@Nullable Project current, @NotNull Project dest) {
     final String settingsValidation = validateSettings(getAdditionalSettings());
     if (settingsValidation != null) {
-      Messages.showErrorDialog(settingsValidation, "Error");
+      OpenApiUtils.safeInvokeLater(() -> {
+        Messages.showErrorDialog(settingsValidation, "Error");
+      });
       try {
         Files.deleteIfExists(Path.of(dest.getBasePath()));
       }