improve builtin timeline custom field option

_layouts/timeline.html

@@ -3,7 +3,7 @@
 layout: page
 custom-foot: js/timeline-js.html
 ---
-{%- assign field = site.data.theme.timeline-field | default: "date" -%}
+{%- assign field = site.data.theme.timeline-field | default: page.timeline-field | default: "date" -%}
 {% if site.data.theme.timeline-child-objects == true %}
 {%- assign items = site.data[site.metadata] | where_exp: 'item','item.objectid' -%}
 {% else %}
@@ -12,7 +12,7 @@
 {%- assign items = items | where_exp: 'item','item[field]' -%}
 {%- assign raw-dates = items | map: field | compact | uniq -%}
 {%- capture clean-years -%}{% for date in raw-dates %}{% if date contains "-" %}{{ date | strip | split: "-" | first }}{% elsif date contains "/" %}{{ date | strip | split: "/" | last }}{% else %}{{ date | strip }}{% endif %}{% unless forloop.last %};{% endunless %}{%- endfor -%}{%- endcapture -%}
-{%- assign uniqueYears = clean-years | remove: " " | replace: ";;",";" | split: ";" | uniq | sort -%}
+{%- assign uniqueYears = clean-years | replace: ";;",";" | split: ";" | compact | uniq | sort -%}
 {%- if site.data.theme.year-navigation -%}
 {%- assign navYears = site.data.theme.year-navigation | split: ";" -%}
 {%- elsif site.data.theme.year-nav-increment -%}