Check if project is disposed in project root manager

[akerimsenol]

We have some integration tests fail with the following stack trace (with different call points ending up here) occasionally. I believe this should at least help mitigate the issue.

        ....
	at com.intellij.openapi.roots.impl.CompilerProjectExtensionImpl.getRootsToWatch(CompilerProjectExtensionImpl.java:84)
	at com.intellij.openapi.roots.impl.CompilerProjectExtensionImpl$MyWatchedRootsProvider.getRootsToWatch(CompilerProjectExtensionImpl.java:134)
	at com.intellij.openapi.roots.impl.ProjectRootManagerComponent.collectWatchRoots(ProjectRootManagerComponent.kt:274)
	at com.intellij.openapi.roots.impl.ProjectRootManagerComponent.addRootsToWatch(ProjectRootManagerComponent.kt:193)
	at com.intellij.openapi.roots.impl.ProjectRootManagerComponent.access$addRootsToWatch(ProjectRootManagerComponent.kt:58)
	at com.intellij.openapi.roots.impl.ProjectRootManagerComponent$registerListeners$1.projectOpened(ProjectRootManagerComponent.kt:135)
	at com.intellij.util.messages.impl.MessageBusImplKt.invokeMethod(MessageBusImpl.kt:655)
	at com.intellij.util.messages.impl.MessageBusImplKt.invokeListener(MessageBusImpl.kt:625)
	```