.zon: If tree has errors then we don't have a root decl..

Any error in a .zon file prevents the creation of the root decl which leads to accessing an undefined value, ie results in a crash.

Also -- any tree.helperFns that call rootDecls aren't ready for .zon

Thank you to NIHKLAS on the Zig Programming Language Discord Server for bringing this to my attention 👋

src/DocumentScope.zig

@@ -815,6 +815,8 @@ noinline fn walkContainerDecl(
     const tracy_zone = tracy.trace(@src());
     defer tracy_zone.end();
 
+    // This is not ready for .zon -- tree.fullContainerDecl on 0 calls tree.rootDecls
+    if (tree.mode == .zon) return; // and node_idx == 0 and tree.errors.len != 0) return;
     const allocator = context.allocator;
     const tags = tree.nodes.items(.tag);
     const token_tags = tree.tokens.items(.tag);

src/Server.zig

@@ -1428,6 +1428,7 @@ fn semanticTokensFullHandler(server: *Server, arena: std.mem.Allocator, request:
     if (server.config.semantic_tokens == .none) return null;
 
     const handle = server.document_store.getHandle(request.textDocument.uri) orelse return null;
+    if (handle.tree.mode == .zon and handle.tree.errors.len != 0) return null;
 
     var analyser = server.initAnalyser(handle);
     defer analyser.deinit();

src/ast.zig

@@ -1698,6 +1698,7 @@ fn iterateChildrenTypeErased(
         },
 
         .root => {
+            if (tree.mode == .zon and tree.errors.len != 0) return;
             for (rootDecls(tree)) |child| {
                 try callback(context, tree, child);
             }

src/features/references.zig

@@ -476,6 +476,7 @@ pub fn referencesHandler(server: *Server, arena: std.mem.Allocator, request: Gen
     defer tracy_zone.end();
 
     const handle = server.document_store.getHandle(request.uri()) orelse return null;
+    if (handle.tree.mode == .zon) return null;
 
     if (request.position().character <= 0) return null;