QTextEdit component crashes when you press the "delete" key

when I use a class which looks like this:

class MyTextEdit : public QTextEdit  {

  void onTextChanged() {   
	QTextCursor copyOfCurrentCursor = textCursor();        //<- this line is the problem
	QTextCharFormat f;
	setCurrentCharFormat(f);    // this is also needed to replicate crash
  }
  
  MyTextEdit() {  
           connect(this,SIGNAL(textChanged()),this,SLOT(onTextChanged()));     
  }
};

I get a crash (when the "delete" key is pressed inside the QTextEdit).

The problem is the "copyOfCurrentCursor";
The destructor deletes the QTextCursorPrivate instance;

when I set a breakpoint in qtextcursor.cpp line 172:

void QTextCursorPrivate::remove()
.
.
} else

after executing the "priv->remove(pos1, pos2-pos1, op);" method
the "this" pointer points to something filled with 0xfeeefeee (windows HeapFree).