Fix crash with error on autocreate savepoint

member variables are initialized in the order they are defined in the
header. We cannot use mError to initialize mSavePointId if the former is
declared after in the header.

References #17535

src/core/qgsvectorlayerundopassthroughcommand.h

@@ -82,8 +82,8 @@ class CORE_EXPORT QgsVectorLayerUndoPassthroughCommand : public QgsVectorLayerUn
     QString errorMessage() const;
 
   private:
-    QString mSavePointId;
     QString mError;
+    QString mSavePointId;
     bool mHasError;
     bool mRecreateSavePoint;
 };