Ensure that failed place startups don't block server startup unless the server is configured to do so

[drivenflywheel]

Mitigates potential NPEs introduced by #598. These NPEs can prevent server startup.

[fbruton]

Recommend creating a unit-test. Here is a test that will cause the current code in the baseline to throw an NPE. Feel free to incorporate and change to your liking.

    @Test
    void testInvisPlaceStartWithNullLocalPlace() throws IOException {
        // setup node, startup, and DirectoryPlace
        EmissaryNode node = new EmissaryNode();
        Startup startup = new Startup(node.getNodeConfigurator(), node);

        try (MockedStatic<DirectoryPlace> dirPlace = Mockito.mockStatic(DirectoryPlace.class)) {

            DirectoryEntry entry = mock(DirectoryEntry.class);
            when(entry.getLocalPlace()).thenReturn(null);

            List<DirectoryEntry> dirEntries = new ArrayList<>();
            dirEntries.add(0, entry);
            
            IDirectoryPlace directoryPlace = mock(IDirectoryPlace.class);
            when(directoryPlace.getEntries()).thenReturn(dirEntries);
            
            dirPlace.when(DirectoryPlace::lookup).thenReturn(directoryPlace);
            
            assertTrue(startup.verifyNoInvisiblePlacesStarted());
        }
        ```

[sambish5]

Looks good to me, if you add the possible unit test I'll review again.

[drivenflywheel]

Unit test added - thanks, @fbruton!

[sambish5]

🚀🚀🚀