[clang-tidy] Fix `modernize-use-scoped-lock` crash on malformed code (#165127)

This code:

```cpp
void f() {
  std::lock_guard<std::mutex> dont_crash {some_nonexistant_variable};
}
```

Generates an AST like this:

```txt
TranslationUnitDecl
`-FunctionDecl <line:3:1, line:5:1> line:3:6 f 'void ()'
  `-CompoundStmt <col:10, line:5:1>
    `-DeclStmt <line:4:3, col:69>
      `-VarDecl <col:3, col:31> col:31 dont_crash 'std::lock_guard<std::mutex>' destroyed
```

Where the `VarDecl` has no initializer. The check doesn't expect this
and crashes.

0 files changed, 0 insertions, 0 deletions