path_form_element_validate executes unnecessary db_select query when only space given for URL Alias.

Problem/Motivation

When adding a node or taxonomy term and the user enters only spaces in "Url Alias" path_form_element_validate executes unnecessary db_select query to check if the alias has been used. path_node_insert, path_node_update, path_taxonomy_term_insert, and path_taxonomy_term_update all trim the $path['alias'] before they check to see if it is empty therefore a spaces only alias will never be saved.

Proposed resolution

Trim the submitted URL alias before checking to see if it is empty. This will eliminate a potential unnecessary db_select execution.

Change

if (!empty($form_state['values']['path']['alias'])) {
    // Trim the submitted value.
    $alias = trim($form_state['values']['path']['alias']);

to

// Trim the submitted value.
  $alias = trim($form_state['values']['path']['alias']);
  if (!empty($alias)) {

I don't know if this is too much of an "corner case" to worry about.
The issue is the same in D7 and D8.
Patch forth coming....

Original report by tedbow