fix: load vsix with no publisher

This is relevant for extension development flow.
Currently when running 'yo code' the extension is created without publisher.
VS code 'Run Extension' launcher is able to run/debug it.
In theia prior to this fix it caused TypeError: Cannot read property 'toLowerCase' of undefined

Signed-off-by: Amiram Wingarten <amiram.wingarten@sap.com>

packages/plugin-ext-vscode/src/node/scanner-vscode.ts

@@ -29,13 +29,15 @@ export class VsCodePluginScanner extends TheiaPluginScanner implements PluginSca
     }
 
     getModel(plugin: PluginPackage): PluginModel {
+        // publisher can be empty on vscode extension development
+        const publisher = plugin.publisher || '';
         const result: PluginModel = {
             packagePath: plugin.packagePath,
             packageUri: FileUri.create(plugin.packagePath).toString(),
             // see id definition: https://github.com/microsoft/vscode/blob/15916055fe0cb9411a5f36119b3b012458fe0a1d/src/vs/platform/extensions/common/extensions.ts#L167-L169
-            id: `${plugin.publisher.toLowerCase()}.${plugin.name.toLowerCase()}`,
+            id: `${publisher.toLowerCase()}.${plugin.name.toLowerCase()}`,
             name: plugin.name,
-            publisher: plugin.publisher,
+            publisher: publisher,
             version: plugin.version,
             displayName: plugin.displayName,
             description: plugin.description,