Fix unexpected preview crash with adding preview condition

[Prokyonn]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets	fixes #issuenum
Related issues/PRs	#issuenum
License	MIT

What's in this PR?

Fixes the preview when the locale is switched to a non existing one in the article detail view.

[Prokyonn]

@alexander-schranz @wachterjohannes that was the best solution I was able to find for the preview condition 😅 it is working but somehow feels a bit wrong, do you have any better suggestion?

[Prokyonn]

@wachterjohannes Checking the locale is only possible, when we also update the PreviewForm.js in sulu/sulu like this:

-    const enablePreview = !previewCondition || jexl.evalSync(previewCondition, this.resourceFormStore.data);
+    const previewData = {
+        ...this.props.router.attributes,
+        ...toJS(this.resourceFormStore.data)
+    };
+    const enablePreview = !previewCondition || jexl.evalSync(previewCondition, previewData);

[alexander-schranz]

is there not a locale and originalLocale returned by the JSON response?
When we add router attributes to the conditoin we maybe should prefix it with __ like we did it with __parent or __webspaces already. So maybe __routeAttributes.

[Prokyonn]

Response json

Unfortunately we do not have a locale or originalLocale only the ghostLocale and this is not helpful.

So should we go with __routeAttributes ?