Fix array conditional

Author: Andy Hanson

src/compiler/program.ts

@@ -358,7 +358,7 @@ namespace ts {
             // load type declarations specified via 'types' argument or implicitly from types/ and node_modules/@types folders
             const typeReferences: string[] = getAutomaticTypeDirectiveNames(options, host);
 
-            if (typeReferences) {
+            if (typeReferences.length) {
                 // This containingFilename needs to match with the one used in managed-side
                 const containingFilename = combinePaths(host.getCurrentDirectory(), "__inferred type names__.ts");
                 const resolutions = resolveTypeReferenceDirectiveNamesWorker(typeReferences, containingFilename);