Add test for #14574 (#18024)

Author: weswigham

tests/cases/fourslash/quickInfoForSyntaxErrorNoError.ts

@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts" />
+
+//// namespace X {
+////     export =
+//// }
+//// X.add/*1*/
+
+// verify there is no crash
+verify.quickInfoAt("1", "any");