dereference clause_clause value, reserve more parser space (#2579)

src/parser/parser.rs

@@ -1287,9 +1287,9 @@ impl<'a, R: CharRead> LexerParser<'a, R> {
         };
 
         // the parser uses conditional indirection in many places so
-        // the reserved size should be at least 3 * term_byte_size
+        // the reserved size should be at least 4 * term_byte_size
         // so all cells are accounted for.
-        let writer = match self.machine_st.heap.reserve(cell_index!(3 * term_byte_size)) {
+        let writer = match self.machine_st.heap.reserve(cell_index!(4 * term_byte_size)) {
             Ok(term) => term,
             Err(_err_loc) => {
                 return Err(ParserError::ResourceError(self.loc_to_err_src()));