Subsubexercies broken when no text in subexercise

[Romern]

This is ok:

\documentclass[fleqn]{solution}

\begin{document}
	\begin{exercise}{}
		\begin{subexercise}[1.5]{}
			Ayy
			\begin{subsubexercise}{}
			\end{subsubexercise}
		\end{subexercise} 
	\end{exercise}
\end{document}

and this breaks:

\documentclass[fleqn]{solution}

\begin{document}
	\begin{exercise}{}
		\begin{subexercise}[1.5]{}
			\begin{subsubexercise}{}
			\end{subsubexercise}
		\end{subexercise} 
	\end{exercise}
\end{document}

Error:

test.tex:6: LaTeX Error: Something's wrong--perhaps a missing \item. [^^I^^I^^I\begin{subsubexercise}{}]