[llvm] [ThinLTO] Fix parsing null aliasee in alias summary (PR #169490)

[via llvm-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Linux-->
# :penguin: Linux x64 Test Results

* 166381 tests passed
* 2869 tests skipped
* 1 test failed

## Failed Tests
(click on a test name to see its output)

### LLVM
<details>
<summary>LLVM.Assembler/thinlto-summary.ll</summary>

```
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 2
/home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llvm-as /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Assembler/thinlto-summary.ll -o - | /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llvm-dis -o - | /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/FileCheck /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Assembler/thinlto-summary.ll
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llvm-as /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Assembler/thinlto-summary.ll -o -
# .---command stderr------------
# | /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llvm-as: /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Assembler/thinlto-summary.ll:49:187: error: use of undefined type id summary '^26'
# | ^19 = gv: (guid: 18, summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0), insts: 4, typeIdInfo: (typeTests: (^26, ^28)))))
# |                                                                                                                                                                                           ^
# `-----------------------------
# error: command failed with exit status: 1
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llvm-dis -o -
# .---command stderr------------
# | /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/llvm-dis: error: file too small to contain bitcode header
# `-----------------------------
# error: command failed with exit status: 1
# executed command: /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/FileCheck /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Assembler/thinlto-summary.ll
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  /home/gha/actions-runner/_work/llvm-project/llvm-project/build/bin/FileCheck /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/test/Assembler/thinlto-summary.ll
# `-----------------------------
# error: command failed with exit status: 2

--

```
</details>

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/169490