Fix: Copy-Paste-Brush with falsy mask

[PierreSchwang]

Overview

Fixes a bug shared on discord.

Description

Use copypaste-brush (//br copypaste) with a falsy mask (e.g. //gmask 0) and select the area via the first click / interact. Output should state, that 0 blocks were copied.. Attempting to paste with that brush, results in no future actions being possible (potentially depending on the queue type).

That's due to the ResizableClipboardBuilder. As the mask did not match any blocks, no blocks were added to the builder. Therefor, on build the default dimensions are used, which results in the region spanning from XYZ Integer.MAX_VALUE to XYZ Integer.MIN_VALUE. The RegionVisitor - called by the ForwardExtentCopy - attempts to load all chunks in that range via the SingleThreadQueueExtent.

The fix is simply using an EmptyClipboard if nothing was being written into the ResizableClipboardBuilder.

### Submitter Checklist
- [x] Make sure you are opening from a topic branch (**/feature/fix/docs/ branch** (right side)) and not your main branch.
- [x] Ensure that the pull request title represents the desired changelog entry.
- [x] New public fields and methods are annotated with `@since TODO`.
- [x] I read and followed the [contribution guidelines](https://github.com/IntellectualSites/.github/blob/main/CONTRIBUTING.md).

[SirYwell]

I think I'd feel more comfortable with the check being in the ResizableClipboardBuilder#build() instead. It's currently not used anywhere else in FAWE, but that's also nothing we ever want to stumble upon again