[lworld] RFR: 8374911: [lworld] C2 fails assert(adr_type != nullptr) failed: source must have adr_type

[Damon Fenacci]

# Issue

The Valhalla test `compiler/valhalla/inlinetypes/TestArrayCopy.java#AlwaysIncrementalInline` crashes intermittently in `ProjNode::adr_type()` when asserting `adr_type != nullptr`.

# Cause

We are in the process of cleaning up an unreacheable subgraph and we get to a situation like this one:

<img width="427" height="336" alt="Screenshot 2026-01-20 at 19 57 31" src="https://github.com/user-attachments/assets/c040b647-0858-4cc9-af68-5a1b05cc58fb" />

We have a Tuple node with top inputs followed by memory projection. Later in the same ideal loop, while running Ideal for the `MemoryMerge` node, we query the type of its memory Proj input, which skips the Tuple here:

https://github.com/openjdk/valhalla/blob/b2f45e0f857fb32bdc36e7b93346ebc967b74736/src/hotspot/share/opto/multnode.cpp#L151-L154

and returns its corresponding input (`2`), which is top (and its `adr_type` returns `nullptr`)

# Fix

We should probably check for `ctrl` being top (for this situation) additionally to `nullptr`.

# Testing

Tier 1-3+
Failing test before and after.

-------------

Commit messages:
 - JDK-8374911: [lworld] C2 fails assert(adr_type != nullptr) failed: source must have adr_type

Changes: https://git.openjdk.org/valhalla/pull/1944/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1944&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374911
  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/1944.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1944/head:pull/1944

PR: https://git.openjdk.org/valhalla/pull/1944