fix(@angular/schematics): fix the null protocol for node-modules-engine-host

Author: hansl

packages/schematics/src/engine/engine.ts

@@ -98,12 +98,6 @@ export class SchematicEngine<CollectionT, SchematicT> implements Engine<Collecti
       case 'host:': return (context: TypedSchematicContext<CollectionT, SchematicT>) => {
         return context.host.map(tree => branch(tree));
       };
-      case '':
-        const fileUrl = parse(format(url));
-        fileUrl.protocol = 'file:';
-        return (context: TypedSchematicContext<CollectionT, SchematicT>) => {
-          return context.engine.createSourceFromUrl(fileUrl)(context);
-        };
       default:
         const hostSource = this._host.createSourceFromUrl(url);
         if (!hostSource) {

packages/schematics/tooling/node-module-engine-host.ts

@@ -122,7 +122,7 @@ export class NodeModulesEngineHost implements EngineHost<NodeModulesCollectionDe
 
   createSourceFromUrl(url: Url): Source | null {
     switch (url.protocol) {
-      case '':
+      case null:
       case 'file:':
         return (context: NodeModulesSchematicContext) => {
           // Resolve all file:///a/b/c/d from the schematic's own path, and not the current