[clang-tools-extra] [clangd] Clangd running with `--experimental-modules-support` crashes when the compilation database is unavailable (PR #153802)

[Chuanqi Xu via cfe-commits]

================
@@ -833,6 +833,8 @@ bool OverlayCDB::setCompileCommand(PathRef File,
 std::unique_ptr<ProjectModules>
 OverlayCDB::getProjectModules(PathRef File) const {
   auto MDB = DelegatingCDB::getProjectModules(File);
+  if (!MDB)
+    return {};
----------------
ChuanqiXu9 wrote:

```suggestion
  if (!MDB) {
    log("Failed to get compilation Database for {0}", File);
    return {};
 }
```

https://github.com/llvm/llvm-project/pull/153802