Check for configuration service

src/sql/workbench/services/notebook/browser/models/cell.ts

@@ -87,13 +87,14 @@ export class CellModel extends Disposable implements ICellModel {
 		// if the fromJson() method was already called and _cellGuid was previously set, don't generate another UUID unnecessarily
 		this._cellGuid = this._cellGuid || generateUuid();
 		this.createUri();
-		this._isCommandExecutionSettingEnabled = this._configurationService.getValue('notebook.allowCommandExecution');
-
-		this._register(this._configurationService.onDidChangeConfiguration(e => {
-			if (e.affectsConfiguration('notebook.allowCommandExecution')) {
-				this._isCommandExecutionSettingEnabled = this._configurationService.getValue('notebook.allowCommandExecution');
-			}
-		}));
+		if (this._configurationService) {
+			this._isCommandExecutionSettingEnabled = this._configurationService.getValue('notebook.allowCommandExecution');
+			this._register(this._configurationService.onDidChangeConfiguration(e => {
+				if (e.affectsConfiguration('notebook.allowCommandExecution')) {
+					this._isCommandExecutionSettingEnabled = this._configurationService.getValue('notebook.allowCommandExecution');
+				}
+			}));
+		}
 	}
 
 	public equals(other: ICellModel) {