[HLSL] DXILOpLowering `cleanupHandleCasts` assertion on uninitialized local resource Store

Compiling an HLSL compute shader that stores through an uninitialized local RWByteAddressBuffer crashes in the DXIL Op Lowering pass with an assertion in cleanupHandleCasts.

Repro:

```hlsl
RWByteAddressBuffer gBuf : register(u0);

[numthreads(1,1,1)]
void main() {
RWByteAddressBuffer buf;
buf.Store(0, 11);
gBuf.Store(0, 42);
}
```

Command: `clang-dxc -T cs_6_0 -Fo out.o input.hlsl`

Stack trace:

```
Assertion failed: isa(Val) && "cast() argument of incompatible type!"
Running pass 'DXIL Op Lowering' on module 'input.hlsl'.

#0 HandleAbort Signals.inc:371
#1 (ucrtbased.dll)
#2 (ucrtbased.dll)
#3 (ucrtbased.dll)
#4 (ucrtbased.dll)
#5 (ucrtbased.dll)
#6 llvm::cast Casting.h:573
#7 OpLowerer::cleanupHandleCasts DXILOpLowering.cpp:181
#8 OpLowerer::lowerIntrinsics DXILOpLowering.cpp:1012
#9 DXILOpLoweringLegacy::runOnModule DXILOpLowering.cpp:1048
#10 MPPassManager::runOnModule LegacyPassManager.cpp:1513
```

Clang version: 23.0.0git (commit 2a2ba99)