diff --git a/.travis.yml b/.travis.yml
index 7c6d399..6518161 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,11 +13,13 @@ addons:
 sudo: required
 
 php:
+  - 7.3
+  - 7.4
   - 8.0
   - 8.1.0
 env:
-  - APPLICATION=ojs BRANCH=main TEST=mysql
-  - APPLICATION=ojs BRANCH=main TEST=pgsql
+  - APPLICATION=ojs BRANCH=stable-3_3_0 TEST=mysql
+  - APPLICATION=ojs BRANCH=stable-3_3_0 TEST=pgsql
 
 install:
   # Prepare OJS environment
diff --git a/templates/frontend/pages/search.tpl b/templates/frontend/pages/search.tpl
index e7aa569..3bbbed8 100644
--- a/templates/frontend/pages/search.tpl
+++ b/templates/frontend/pages/search.tpl
@@ -59,6 +59,7 @@
 				<h2>{translate key="plugins.themes.healthSciences.search.params"}</h2>
 
 				{capture name="searchFormUrl"}{url escape=false}{/capture}
+				{assign var=formUrlParameters value=[]}{* Prevent Smarty warning *}
 				{$smarty.capture.searchFormUrl|parse_url:$smarty.const.PHP_URL_QUERY|parse_str:$formUrlParameters}
 				<form class="form-search" method="get" action="{$smarty.capture.searchFormUrl|strtok:"?"|escape}">
 					{foreach from=$formUrlParameters key=paramKey item=paramValue}