Correct failure to remove empty fluid stacks from MEPatternPartMachine

[bk5115545]

What

We're playing Monifactory and noticed that ME Pattern Buffers that use Fluids sometimes jam. The jam is much more likely when multiple fluids are in play across multiple patterns. When crafts jam, we notice that 0 mb of Air is left inside the ME Pattern Buffer. We suspect that it is causing recipes to not be crafted because they do not use Air - or maybe that every fluidInventory is already full of another fluid.

It could also just be visual though.

We only see the Air after pressing the Return button which maps to the refund() function

Implementation Details

This change also removes empty fluids from the internal fluidInventory when they are empty.

Outcome

Should cause empty fluid stacks to be removed from ME Pattern Buffers

Additional Information

This section is for screenshots to demonstrate any GUI or rendering changes, or any other additional information that reviewers should be aware of.

Potential Compatibility Issues

This section is for defining possible compatibility issues. It must be used when there are API changes, item/block/material/machine changes, or recipe changes.

Please fill in as much useful information as possible. Also, please remove all unused sections, including this and the other explanations.

[bk5115545]

Possibly related: #2227 #2110

And I think the logic in onPatternChange looks a bit sus. I noticed that picking up and replacing any pattern always either voids or returns one pending stack though not all stacks. This is hopefully a separate issue though and anyone else is welcome to dig on that.

[krossgg]

The empty fluid stacks are not the reason for the pattern buffer issues - there are some other major problems. It has been reworked in #2544 which is planned for 1.7.0, the next major release. For that reason, I am closing this PR, but thank you for your contribution.