feat: prevent race condition dev-only error (#2789)

* fix(RouterView): guard against null instance when assigning __vrv_devtools

* Apply suggestion from @posva

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Co-authored-by: Eduardo San Martin Morote <posva@users.noreply.github.com>

Author: meihao550

packages/router/src/RouterView.ts

@@ -196,7 +196,9 @@ export const RouterViewImpl = /*#__PURE__*/ defineComponent({
 
         internalInstances.forEach(instance => {
           // @ts-expect-error
-          instance.__vrv_devtools = info
+          // to prevent possible race condition in SSR
+          // https://github.com/vuejs/router/pull/2789
+          if (instance) instance.__vrv_devtools = info
         })
       }