Only include default preview frame styles if no preview styles are provided

BREAKING_CHANGES.md

@@ -9,6 +9,10 @@ BREAKING_CHANGES
 - media path changed from `string | string[]` to `{ path: string | string[], alt?: string }`
 - Nested collections, meta config moved into nested config.
 
+CHANGES
+
+- Default styles are now provided in the preview frame. If you provide your own via `registerPreviewStyle`, then these default styles will not be included.
+
 ADDED
 - `forSingleList` - Allows for changing styles for single list items
 

packages/core/src/components/entry-editor/editor-preview-pane/EditorPreviewPane.tsx

@@ -112,18 +112,20 @@ const PreviewPane = (props: TranslatedProps<EditorPreviewPaneProps>) => {
 
   const { widgetFor, widgetsFor } = useWidgetsFor(config, collection, fields, entry);
 
-  const previewStyles = useMemo(
-    () => [
-      ...getPreviewStyles().map((style, i) => {
-        if (style.raw) {
-          return <style key={i}>{style.value}</style>;
-        }
-        return <link key={i} href={style.value} type="text/css" rel="stylesheet" />;
-      }),
-      <style key="global">{FrameGlobalStyles}</style>,
-    ],
-    [],
-  );
+  const previewStyles = useMemo(() => {
+    const styles = getPreviewStyles().map((style, i) => {
+      if (style.raw) {
+        return <style key={i}>{style.value}</style>;
+      }
+      return <link key={i} href={style.value} type="text/css" rel="stylesheet" />;
+    });
+
+    if (styles.length === 0) {
+      return <style key="global">{FrameGlobalStyles}</style>;
+    }
+
+    return styles;
+  }, []);
 
   const previewComponent = useMemo(
     () => getPreviewTemplate(selectTemplateName(collection, entry.slug)) ?? EditorPreview,