Made empty arrays behave the same as no array.

src/govuk/components/date-input/template.njk

@@ -7,7 +7,7 @@
    aria-describedby – for example hints or error messages -#}
 {% set describedBy = params.fieldset.describedBy if params.fieldset.describedBy else "" %}
 
-{% if params.items %}
+{% if params.items | length %}
   {% set dateInputItems = params.items %}
 {% else %}
   {% set dateInputItems = [

src/govuk/components/footer/template.njk

@@ -1,12 +1,12 @@
 <footer class="govuk-footer {{ params.classes if params.classes }}" role="contentinfo"
         {%- for attribute, value in params.attributes %} {{attribute}}="{{value}}"{% endfor %}>
   <div class="govuk-width-container {{ params.containerClasses if params.containerClasses }}">
-    {% if params.navigation %}
+    {% if params.navigation | length %}
       <div class="govuk-footer__navigation">
         {% for nav in params.navigation %}
           <div class="govuk-footer__section">
             <h2 class="govuk-footer__heading govuk-heading-m">{{ nav.title }}</h2>
-            {% if nav.items %}
+            {% if nav.items | length %}
               {% set listClasses %}
                 {% if nav.columns %}
                   govuk-footer__list--columns-{{ nav.columns }}
@@ -33,7 +33,7 @@
       <div class="govuk-footer__meta-item govuk-footer__meta-item--grow">
         {% if params.meta %}
           <h2 class="govuk-visually-hidden">{{ params.meta.visuallyHiddenTitle | default("Support links") }}</h2>
-          {% if params.meta.items %}
+          {% if params.meta.items | length %}
             <ul class="govuk-footer__inline-list">
               {% for item in params.meta.items %}
                 <li class="govuk-footer__inline-list-item">

src/govuk/components/summary-list/template.njk

@@ -10,7 +10,7 @@
 {# Determine if we need 2 or 3 columns #}
 {% set anyRowHasActions = false %}
 {% for row in params.rows %}
-  {% set anyRowHasActions = true if row.actions.items else anyRowHasActions %}
+  {% set anyRowHasActions = true if row.actions.items | length else anyRowHasActions %}
 {% endfor -%}
 
 <dl class="govuk-summary-list {%- if params.classes %} {{ params.classes }}{% endif %}"{% for attribute, value in params.attributes %} {{attribute}}="{{value}}"{% endfor %}>

src/govuk/components/tabs/template.njk

@@ -6,7 +6,7 @@
   <h2 class="govuk-tabs__title">
     {{ params.title | default ("Contents") }}
   </h2>
-  {% if(params.items) %}
+  {% if(params.items | length) %}
   <ul class="govuk-tabs__list">
     {% for item in params.items %}
       {% if item %}