Undo removal of "can be NULL" remark

Also remove a unecessary empty line.

src/keybindings.c

@@ -217,7 +217,7 @@ GeanyKeyBinding *keybindings_set_item(GeanyKeyGroup *group, gsize key_id,
  * @param kf_name Key name for the configuration file, such as @c "menu_new".
  * @param label Label used in the preferences dialog keybindings tab. May contain
  * underscores - these won't be displayed.
- * @param menu_item @nullable Optional widget to set an accelerator for.
+ * @param menu_item @nullable Optional widget to set an accelerator for, or @c NULL.
  * @param cb @nullable New-style callback to be called when activated, or @c NULL to use the group callback.
  * @param pdata Plugin-specific data passed back to the callback @a cb.
  * @param destroy_notify Function that is invoked to free the plugin data when not needed anymore.

src/utils.c

@@ -1652,7 +1652,7 @@ const gchar *utils_get_default_dir_utf8(void)
  *  @param env The child's environment, or @c NULL to inherit parent's.
  *  @param flags Ignored.
  *  @param child_setup @girskip Ignored.
- *  @param user_data Ignored.
+ *  @param user_data @girskip Ignored.
  *  @param std_out The return location for child output, or @c NULL.
  *  @param std_err The return location for child error messages, or @c NULL.
  *  @param exit_status The child exit status, as returned by waitpid(), or @c NULL.
@@ -1955,7 +1955,6 @@ static gboolean str_in_array(const gchar **haystack, const gchar *needle)
  *
  * The argument list must be @c NULL-terminated.
  *
- *
  * @param exclude_vars @c NULL-terminated array of variable names to exclude.
  * @param first_varname Name of the first variable to copy into the new array.
  * @param ... Key-value pairs of variable names and values, @c NULL-terminated.