message: Don't create launch.json for no select process
  This PR fixes resolveDebugConfigurationWithSubstitutedVariables to
  return null when user does not select a process in the process selection
  dialog.
diff: @@ -55,7 +55,8 @@ export class DotnetDebugConfigurationProvider implements vscode.DebugConfigurati
  }
  else
  {
  - throw new Error("No process was selected.");
  + vscode.window.showErrorMessage("No process was selected.", { modal: true });
  + return undefined;
  }
  }
  