cell_index is not initialized when a table cell is created using cmark_node_new_with_ext() #360
Description
Starting with commit 5e8ad61 a table cell keeps track of its index. When creating a table cell with cmark_node_new_with_ext(), the cell_index value is not initialized anywhere. This will cause functions like cmark_render_html() and cmark_render_xml() to crash.
Example code:
#include <string.h>
#include <cmark-gfm.h>
#include <cmark-gfm-core-extensions.h>
const char* doc_str = "\n"
"| foo | bar |\n"
"| --- | --- |\n"
"| baz | bim |\n"
"";
int main() {
cmark_gfm_core_extensions_ensure_registered();
cmark_parser* parser = cmark_parser_new(0);
cmark_parser_attach_syntax_extension(parser, cmark_find_syntax_extension("table"));
cmark_parser_feed(parser, doc_str, strlen(doc_str));
cmark_node* doc = cmark_parser_finish(parser);
const char* html = cmark_render_html(doc, 0, 0);
printf("%s\n", html);
const char* xml = cmark_render_xml(doc, 0);
printf("%s\n", xml);
cmark_node* table = cmark_node_first_child(doc);
cmark_node* header = cmark_node_first_child(table);
cmark_node* cell = cmark_node_first_child(header);
printf("cell is a '%s'\n", cmark_node_get_type_string(cell));
cmark_node* new_cell = cmark_node_new_with_ext(cmark_node_get_type(cell), cmark_node_get_syntax_extension(cell));
printf("new_cell is a '%s'\n", cmark_node_get_type_string(new_cell));
cmark_node_prepend_child(header, new_cell);
cmark_node_unlink(cell);
const char* html2 = cmark_render_html(doc, 0, 0);
printf("%s\n", html2);
const char* xml2 = cmark_render_xml(doc, 0);
printf("%s\n", xml2);
}