[FIX] component: crashes if no template can be found

closes #178

src/component.ts

@@ -458,7 +458,9 @@ export class Component<T extends Env, Props extends {}, State extends {}> {
           p = p.__proto__;
         }
         if (p === Component) {
-          this.template = "default";
+          throw new Error(
+            `Could not find template for component "${this.constructor.name}"`
+          );
         } else {
           tmap[name] = template;
           this.template = template;

src/qweb_core.ts

@@ -149,7 +149,6 @@ export class QWeb {
     if (data) {
       this.addTemplates(data);
     }
-    this.addTemplate("default", "<div></div>");
   }
 
   static addDirective(directive: Directive) {