fix problem with using "toLowerCase()" function on non-string  values
fix problem with using "toLowerCase()" function on non-string  values

ssuperczynski/ngx-easy-table,ssuperczynski/ng2-easy-table,ssuperczynski/ngx-easy-table,ssuperczynski/ngx-easy-table,ssuperczynski/ng2-easy-table,ssuperczynski/ng2-easy-table,ssuperczynski/ngx-easy-table