目录中的章节标题重复问题

Question

当该部分或其子部分被删除时，下一个子部分就是标题重复的部分，以下是该项目这部分的代码：

\section{Backend design}
\subsection{Firebase authentication}

In the backend development chapter. The Auth-service.dart sign-up and sign-in, error 
handling and sign-out functionalities. AuthService().logout().

\subsection{Complete and edit profile backend}
\paragraph{}
After choosing to register for a new account on the app..

\subsection{Main.dart and global variables}
\paragraph{}
Every Flutter app starts by firstly executing code on the main.dart class...

\subsection{Firebase Firestore}
\paragraph{}
The Naffsi app uses a Firebase Firestore NoSQL database.executing tasks in a parallel 
manner independent of increased traffic \cite{firestoreSynchro}

\begin{figure}[H]
     \centering
     \includegraphics[width=9.62cm]{Figures/Chapter5/snapshot.png}
     \caption{Firestore snapshot code example}
     \label{}
\end{figure}

一些错误是：

Extra \fi.
Undefined control sequence.
Overfull \hbox (18.67542pt too wide) in paragraph at lines 600--601

这些是帮助重现的相关信息

% TABLE OF CONTENTS, FIGURES AND TABLES
% ---------------------------

\newcommand{\thesisTOF}{
    \iftotalfigures
    \cleardoublepage
    \listoffigures
\fi
}

\newcommand{\thesisTOT}{
\iftotaltables
    \cleardoublepage
    \listoftables
\fi
}

\newcommand{\thesisTables}{
\cleardoublepage
\renewcommand{\contentsname}{Table of Contents}
\setcounter{tocdepth}{3}
{\setstretch{1.25}
    \tableofcontents
    \thesisTOF
    \thesisTOT
}

\setlength{\abovedisplayskip}{1pt}
\setlength{\belowdisplayskip}{15pt}
}

\RequirePackage{amsmath}
% --
\RequirePackage{ifthen}
\RequirePackage{xkeyval}
\RequirePackage[dvipsnames]{xcolor}
\RequirePackage[T1]{fontenc} % font types and character 
 verification
\RequirePackage[UKenglish]{babel}
\RequirePackage[UKenglish]{isodate}
\RequirePackage[utf8]{inputenc}
\RequirePackage{xparse}
\RequirePackage{graphicx}
\RequirePackage{longtable}
\RequirePackage{blindtext}
\RequirePackage{parskip}
\RequirePackage{setspace}
\RequirePackage{geometry}
\RequirePackage{layout}
\RequirePackage{courier}
\RequirePackage{subcaption}
\RequirePackage{url}
\RequirePackage{hyperref}
\RequirePackage[table,figure]{totalcount}
\RequirePackage{french}
\RequirePackage{appendix}
% -----------------
\RequirePackage{csquotes}
\RequirePackage{titlesec}
\RequirePackage{datetime2}
\RequirePackage{fancyhdr}
\RequirePackage{lmodern}

还

\usepackage{french}
\usepackage{booktabs}
\usepackage{float}
\usepackage{tikz}
\usepackage{tabto}
\usepackage{subfigure}
\usepackage{subcaption}
\usepackage{enumitem}
\usepackage{hyperref}