Problem with equation inside figure

Question

I am co-writing a paper in linguistics on Overleaf. When I download the tex-file and try to compile it locally on the computer (Editor Winedt), I get an error mistake that is not present in Overleaf, where everything compiles correctly. It is clearly related to an equation environment inside a figure. I do not manage to find a solution.

Here's a relatively minimal working example. The error message is :

! Missing $ inserted.
<inserted text> 

---

\documentclass{article}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[normalem]{ulem} 
\usepackage{booktabs}
\usepackage{amsmath}

\begin{document}

Some text

\begin{figure} \centering
\caption{A feature bundle on C$^0$}
\vspace{0,5cm}
\label{lex}

\begin{equation*}

\left  ( \begin{array}{lll} \textrm{C$^0$[Fin], [EPP]} & [Focus] & [Topic] \\ & [Contrastive] & [Contrastive] \\ & [Mirative] & [Shifting] \\ & [\ldots] & [\ldots]
\end{array}
 \right )

\end{equation*}
 \vspace{0,5cm}
\end{figure}

\end{document} 

Answer 1

As @samcarter_is_at_topanswers.xyz has already noted in a comment, blank lines aren't allowed in a display math environment. The fact that your test document supposedly compiles successfully on Overleaf is almost certainly due to Overleaf doing an excellent [!] job hiding LaTeX warning and other messages from users.

I'd go further than just eliminate the blank lines, though. Specifically, I'd (a) use inline math mode instead of display math mode and (b) employ a tabular environment instead of an array environment because the words in the 4x3 array should be typeset in text mode, not math mode.

A separate issue: Is it essential that the tabular/array material be surrounded by round parentheses? Would simple vertical lines on either side of the tabular/array material do just a well? If so, you could get rid of the math-y setup entirely and replace \begin{tabular}{lll} with \begin{tabular}{|lll|}, as is demonstrated in the lower half of the following screenshot. (For that matter, does the table really need to be surrounded by either parentheses or vertical lines?)

\documentclass{article}
\usepackage[english]{babel}
%\usepackage[utf8]{inputenc} % that's the default nowadays
\usepackage[T1]{fontenc}
\usepackage[normalem]{ulem} 
\usepackage{booktabs}
\usepackage{amsmath}

\begin{document}
Some text\dots

\begin{figure}[h]
\centering

\caption{A feature bundle on $C^0$}\label{lex}
\vspace*{5mm}

%% a 'tabular' env. flanked by tall math-mode parentheses
$\left( 
\begin{tabular}{lll} 
$C^0$[Fin], [EPP] & [Focus] & [Topic] \\ 
   & [Contrastive] & [Contrastive] \\ 
   & [Mirative]    & [Shifting] \\ 
   & [\ldots]      & [\ldots] \\
\end{tabular}
\right)$

\vspace*{0.5cm}

%% just a 'tabular' env. flanked by vertical bars
\begin{tabular}{|lll|} 
$C^0$[Fin], [EPP] & [Focus] & [Topic] \\ 
   & [Contrastive] & [Contrastive] \\ 
   & [Mirative]    & [Shifting] \\ 
   & [\ldots]      & [\ldots] \\
\end{tabular}

\end{figure}

Some more text\dots
\end{document} 

Answer 2

Define your own environment.

Also, if you want the caption above the material, tell LaTeX so, rather than adding random spaces.

\documentclass{article}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[normalem]{ulem} 
\usepackage{booktabs}
\usepackage{amsmath}
\usepackage{caption}

\captionsetup[figure]{position=top}

\newenvironment{ptabular}
 {$\left(\hspace{-\tabcolsep}\tabular}{\endtabular\hspace{-\tabcolsep}\right)$}

\begin{document}

Some text

\begin{figure}[htp]
\centering

\caption{A feature bundle on C$^0$}
\label{lex}

\begin{ptabular}{lll}
C$^0$[Fin], [EPP] & [Focus]       & [Topic] \\
\addlinespace
                  & [Contrastive] & [Contrastive] \\
\addlinespace
                  & [Mirative]    & [Shifting] \\
\addlinespace
                  & [\ldots]      & [\ldots]
\end{ptabular}
\end{figure}

Some other text

\end{document}