debug: fall back to explicit provided config if no selected name

Fixes #135899

src/vs/workbench/contrib/debug/browser/debugConfigurationManager.ts

@@ -376,7 +376,11 @@ export class ConfigurationManager implements IConfigurationManager {
 		}
 
 		const names = launch ? launch.getConfigurationNames() : [];
-		this.getSelectedConfig = () => Promise.resolve(this.selectedName ? launch?.getConfiguration(this.selectedName) : undefined);
+		this.getSelectedConfig = () => {
+			const selected = this.selectedName ? launch?.getConfiguration(this.selectedName) : undefined;
+			return Promise.resolve(selected || config);
+		};
+
 		let type = config?.type;
 		if (name && names.indexOf(name) >= 0) {
 			this.setSelectedLaunchName(name);