rustdoc: don't panic on a nested use group with no path prefix

src/librustdoc/clean/mod.rs

@@ -3221,7 +3221,7 @@ fn clean_use_statement<'tcx>(
             for (tree, hir_id, def_id) in items {
                 let mut segments = path.segments.to_vec();
                 segments.extend(tree.prefix.segments.iter());
-                if segments.last().unwrap().ident.name == kw::SelfLower {
+                if segments.last().is_some_and(|seg| seg.ident.name == kw::SelfLower) {
                     segments.pop();
                 }
                 let path = hir::UsePath {

tests/rustdoc-ui/ice-nested-use-without-prefix-164158-edition2015.rs

@@ -0,0 +1,9 @@
+//@ check-pass
+//@ edition: 2015
+
+// Regression test for <https://github.com/rust-lang/rust/issues/164158>.
+// Nested glob use with no path prefix (edition 2015 form from review).
+
+mod what {
+    use {*};
+}

tests/rustdoc-ui/ice-nested-use-without-prefix-164158.rs

@@ -0,0 +1,14 @@
+//@ check-pass
+//@ edition: 2021
+
+// Regression test for <https://github.com/rust-lang/rust/issues/164158>.
+// A nested use group with no path in front of it made rustdoc panic.
+
+use {{}};
+
+pub mod inner {
+    pub struct S;
+    pub struct T;
+}
+
+pub use {inner::S, {inner::T}};