Handle undefined in indent helper (#38217)

* Handle undefined in indent helper

Telemetry shows that it's called with undefined (probably `stderr` in an
error scenario?).

* Add undefined to parameter type

Author: amcasey

src/typingsInstaller/nodeTypingsInstaller.ts

@@ -246,7 +246,9 @@ namespace ts.server.typingsInstaller {
     const installer = new NodeTypingsInstaller(globalTypingsCacheLocation!, typingSafeListLocation!, typesMapLocation!, npmLocation, validateDefaultNpmLocation, /*throttleLimit*/5, log); // TODO: GH#18217
     installer.listen();
 
-    function indent(newline: string, str: string): string {
-        return `${newline}    ` + str.replace(/\r?\n/, `${newline}    `);
+    function indent(newline: string, str: string | undefined): string {
+        return str && str.length
+            ? `${newline}    ` + str.replace(/\r?\n/, `${newline}    `)
+            : "";
     }
 }