[release/8.0-staging] [mono][hotreload] Ignore if we receive an empty update.

[github-actions]

Backport of #120333 to release/8.0-staging

/cc @thaystg

Customer Impact

• Customer reported
• Found internally

This change was initially backported to .NET 10 and 9 back in October:

10 - #120334
9 - #120335

We didn't think we would need it in .NET 8, but that turned out to not be the case.

This change fixes a problem with hot reload on blazor webassembly where two updates are sent to the runtime at the same time and the runtime asserts. This was previously an unsupported scenario, but recent up stack changes altered the behavior. The plan is to fix both the up stack behavior and in runtime as a defense in depth. The reasoning is that one of the two updates sent to runtime contains no IL. We can look at that one and safely ignore it.

Regression

• Yes
• No

Not in runtime at least. This was not a supported scenario, but was trigged via a VS level change.

[If yes, specify when the regression was introduced. Provide the PR or commit if known.]

Testing

Manual before and after testing

[How was the fix verified? How was the issue missed previously? What tests were added?]

Risk

Low

[High/Medium/Low. Justify the indication by mentioning how risks were measured and addressed.]

IMPORTANT: If this backport is for a servicing release, please verify that:

• For .NET 8 and .NET 9: The PR target branch is release/X.0-staging, not release/X.0.
• For .NET 10+: The PR target branch is release/X.0 (no -staging suffix).

Package authoring no longer needed in .NET 9

IMPORTANT: Starting with .NET 9, you no longer need to edit a NuGet package's csproj to enable building and bump the version.
Keep in mind that we still need package authoring in .NET 8 and older versions.