fix(es/transformer): Fix missing var declaration in nullish coalescing with spreads (#11377)

## Summary

Fixes #11375

The nullish coalescing operator (`??`) was missing the `var` declaration
for the temporary variable when used in functions with spread
parameters.

### Root Cause

The bug was in the `exit_stmt` function in the nullish coalescing
transformer. When exiting a statement, it was incorrectly restoring the
statement pointer:
- It popped the current statement from the stack
- Then set `stmt_ptr` to the popped value (the statement we just exited)

This meant `stmt_ptr` was pointing to the wrong statement when trying to
inject variable declarations for nested expressions.

### The Fix

Changed the `exit_stmt` function to correctly restore the parent
statement pointer by using `last().copied()` on the stack after popping.

### Before
```javascript
// Missing var declaration
(_props_children = props.children) !== null && _props_children !== void 0 ? _props_children : props.label
```

### After
```javascript
var _props_children;
(_props_children = props.children) !== null && _props_children !== void 0 ? _props_children : props.label
```

## Test plan

- ✅ Added test case for issue #11375
- ✅ All tests pass: `cargo test -p swc --test tsc` (4580 tests)
- ✅ All tests pass: `cargo test -p swc --test projects` (860 tests)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Sonnet 4.5 (1M context) <[email protected]>

Author: kdy1

.changeset/eight-chicken-sneeze.md

@@ -0,0 +1,6 @@
+---
+swc_core: patch
+swc_ecma_transformer: patch
+---
+
+fix(es/transformer): Fix missing var declaration in nullish coalescing with spreads

crates/swc/tests/fixture/issues-11xxx/11375/input/.swcrc

@@ -0,0 +1,19 @@
+{
+    "jsc": {
+      "parser": {
+        "syntax": "typescript",
+        "tsx": true
+      },
+      "target": "es5",
+      "loose": false,
+      "minify": {
+        "compress": false,
+        "mangle": false
+      }
+    },
+    "module": {
+      "type": "es6"
+    },
+    "minify": false,
+    "isModule": true
+  }

crates/swc/tests/fixture/issues-11xxx/11375/input/index.tsx

@@ -0,0 +1,14 @@
+export default function DropdownNavbarItemDesktop({
+    items,
+    ...props
+  }) {
+    return (
+      <div>
+        <NavbarNavLink
+          onClick={props.to ? undefined : (e) => e.preventDefault()}
+        >
+          {props.children ?? props.label}
+        </NavbarNavLink>
+      </div>
+    );
+  }

crates/swc/tests/fixture/issues-11xxx/11375/output/index.tsx

@@ -0,0 +1,12 @@
+import { _ as _object_without_properties } from "@swc/helpers/_/_object_without_properties";
+export default function DropdownNavbarItemDesktop(_0) {
+    var items = _0.items, props = _object_without_properties(_0, [
+        "items"
+    ]);
+    var _props_children;
+    return React.createElement("div", null, React.createElement(NavbarNavLink, {
+        onClick: props.to ? undefined : function(e) {
+            return e.preventDefault();
+        }
+    }, (_props_children = props.children) !== null && _props_children !== void 0 ? _props_children : props.label));
+}

crates/swc_ecma_transformer/src/es2020/nullish_coalescing.rs

@@ -80,8 +80,8 @@ impl VisitMutHook<TraverseCtx> for NullishCoalescingPass {
     }
 
     fn exit_stmt(&mut self, _stmt: &mut Stmt, _ctx: &mut TraverseCtx) {
-        self.stmt_ptr = None;
-        self.stmt_ptr = self.stmt_ptr_stack.pop();
+        self.stmt_ptr_stack.pop();
+        self.stmt_ptr = self.stmt_ptr_stack.last().copied();
     }
 }