Fix globalThis completions (#30441)

* Fix, but with test not quite right

* Add missing completions to test

* Remove out-of-date comment

src/services/completions.ts

@@ -890,7 +890,9 @@ namespace ts.Completions {
                         }
 
                         // If the module is merged with a value, we must get the type of the class and add its propertes (for inherited static methods).
-                        if (!isTypeLocation && symbol.declarations.some(d => d.kind !== SyntaxKind.SourceFile && d.kind !== SyntaxKind.ModuleDeclaration && d.kind !== SyntaxKind.EnumDeclaration)) {
+                        if (!isTypeLocation &&
+                            symbol.declarations &&
+                            symbol.declarations.some(d => d.kind !== SyntaxKind.SourceFile && d.kind !== SyntaxKind.ModuleDeclaration && d.kind !== SyntaxKind.EnumDeclaration)) {
                             addTypeProperties(typeChecker.getTypeOfSymbolAtLocation(symbol, node));
                         }
 

tests/cases/fourslash/completionAfterGlobalThis.ts

@@ -0,0 +1,12 @@
+/// <reference path='fourslash.ts'/>
+
+////globalThis./**/
+
+verify.completions({
+    marker: "",
+    exact: [
+        { name: "globalThis", kind: "module" },
+        ...completion.globalsVars,
+        { name: "undefined", kind: "var" }
+    ]
+});