Segment fails to unmap when closing a very small GOL

[clarisma]

OS: Windows 10

Attempting to truncate a GOL to its true size (16 KB) during closing fails:

Error while closing file (The requested operation cannot be performed on a file with a user-mapped section open)

However, Store.unmapSegments() completes successfully.

The problem does not manifest on other small-ish GOLs, such as Monaco (~ 1 MB)

[clarisma]

Problem is caused by Buildcontext.getTileCatalog(), which reads the tile index using its own MappedByteBuffer. This MappedByteBuffer is only unmapped when it is garbage collected -- but when building small files, there is not enough memory pressure, and hence GC never happens.

Proposed solution: Explicitly unmap the segment after use.