scanner: Fail on empty enumerations

Without this patch, the scanner would generate invalid C which wouldn't
compile anyway, so lets be nice and fail earlier and point out where the
error is.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: David Fort <contact@hardening-consulting.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/scanner.c

@@ -552,6 +552,10 @@ end_element(void *data, const XML_Char *name)
 		   strcmp(name, "event") == 0) {
 		ctx->message = NULL;
 	} else if (strcmp(name, "enum") == 0) {
+		if (wl_list_empty(&ctx->enumeration->entry_list)) {
+			fail(&ctx->loc, "enumeration %s was empty",
+			     ctx->enumeration->name);
+		}
 		ctx->enumeration = NULL;
 	}
 }