Segfault when running firtool 1.60.0, standalone example included

```
$ firtool --version
LLVM (http://llvm.org/):
LLVM version 18.0.0git
Optimized build.
CIRCT firtool-1.60.0
```

untar [firtool-crash.tar.gz](https://github.com/llvm/circt/files/13859206/firtool-crash.tar.gz)

Run:

```
firtool --format=fir --export-module-hierarchy --verify-each=true --warn-on-unprocessed-annotations --disable-annotation-classless --disable-annotation-unknown --mlir-timing --lowering-options=emittedLineLength=2048,noAlwaysComb,disallowLocalVariables,verifLabels,locationInfoStyle=wrapInAtSquareBracket,disallowPackedArrays,omitVersionComment --repl-seq-mem-file=megaboom/mems.conf --annotation-file=anno.json --strip-debug-info --strip-fir-debug-info --extract-test-code --split-verilog --disable-all-randomization -o megaboom/ ChipLikeMegaBoomConfig.sfc.fir
```

Output:

```
ChipLikeMegaBoomConfig.sfc.fir:2:1: warning: unprocessed annotation:'firrtl.transforms.NoCircuitDedupAnnotation$' still remaining after LowerToHW
circuit TestHarness :
^
ChipLikeMegaBoomConfig.sfc.fir:2:1: warning: unprocessed annotation:'logger.LogLevelAnnotation' still remaining after LowerToHW
circuit TestHarness :
^
ChipLikeMegaBoomConfig.sfc.fir:43120:3: warning: unprocessed annotation:'freechips.rocketchip.util.RegFieldDescMappingAnnotation' still remaining after LowerToHW
module PeripheryBus :
^
ChipLikeMegaBoomConfig.sfc.fir:282740:3: warning: unprocessed annotation:'freechips.rocketchip.util.RetimeModuleAnnotation' still remaining after LowerToHW
module IntToFP :
^
ChipLikeMegaBoomConfig.sfc.fir:557900:3: warning: unprocessed annotation:'freechips.rocketchip.util.ParamsAnnotation' still remaining after LowerToHW
module BoomTile :
^
ChipLikeMegaBoomConfig.sfc.fir:696542:3: warning: unprocessed annotation:'freechips.rocketchip.util.AddressMapAnnotation' still remaining after LowerToHW
module DigitalTop :
^
generators/rocket-chip/src/main/scala/util/DescribedSRAM.scala:17:26: warning: unprocessed annotation:'freechips.rocketchip.util.SRAMAnnotation' still remaining after LowerToHW
PLEASE submit a bug report to https://github.com/llvm/circt and include the crash backtrace.
Segmentation fault (core dumped)
```

Extract firtool-crash.tar.gz and run the provided firtool command against ChipLikeMegaBoomConfig.sfc.fir, including the referenced megaboom/mems.conf and anno.json. Start by capturing the crash backtrace after the warnings. Done means the standalone example no longer segfaults and the command completes successfully.

Written by the indexing model from the issue text.