Fix anyref table export in empty modules

This commit fixes an issue previously introduced around handling the
anyref table, gracefully handling the case where the source module
doesn't actually use the anyref table at all, meaning that the logic
around initializing it can be entirely skipped.

crates/cli-support/src/webidl/mod.rs

@@ -623,6 +623,24 @@ impl<'a> Context<'a> {
         if !self.anyref_enabled {
             return Ok(());
         }
+
+        // Make sure to export the `anyref` table for the JS bindings since it
+        // will need to be initialized. If it doesn't exist though then the
+        // module must not use it, so we skip it.
+        let table = self
+            .module
+            .tables
+            .iter()
+            .find(|t| match t.kind {
+                walrus::TableKind::Anyref(_) => true,
+                _ => false,
+            });
+        let table = match table {
+            Some(t) => t.id(),
+            None => return Ok(()),
+        };
+        self.module.exports.add("__wbg_anyref_table", table);
+
         let ty = self.module.types.add(&[], &[]);
         let (import, import_id) = self.module.add_import_func(
             PLACEHOLDER_MODULE,
@@ -640,6 +658,7 @@ impl<'a> Context<'a> {
             None => import,
         });
         self.bind_intrinsic(import_id, Intrinsic::InitAnyrefTable)?;
+
         Ok(())
     }