Make sure not to concatenate non-existent files. (#1308)

- Logs an error message when missing files are encountered.

module/VuFindTheme/src/VuFindTheme/View/Helper/ConcatTrait.php

@@ -145,10 +145,10 @@ trait ConcatTrait
 
     /**
      * Initialize class properties related to concatenation of resources.
-     * All of the elements to be concatenated into ($this->concatItems)
-     * and those that need to remain on their own ($this->otherItems).
+     * All of the elements to be concatenated into groups and
+     * and those that need to remain on their own special group 'other'.
      *
-     * @return void
+     * @return bool True if there are items
      */
     protected function filterItems()
     {
@@ -167,10 +167,23 @@ trait ConcatTrait
                 continue;
             }
 
+            $path = $this->getFileType() . '/' . $this->getResourceFilePath($item);
             $details = $this->themeInfo->findContainingTheme(
-                $this->getFileType() . '/' . $this->getResourceFilePath($item),
+                $path,
                 ThemeInfo::RETURN_ALL_DETAILS
             );
+            // Deal with special case: $path was not found in any theme.
+            if (null === $details) {
+                $errorMsg = "Could not find file '$path' in theme files";
+                method_exists($this, 'logError')
+                    ? $this->logError($errorMsg) : error_log($errorMsg);
+                $this->groups[] = [
+                    'other' => true,
+                    'item' => $item
+                ];
+                $groupTypes[] = 'other';
+                continue;
+            }
 
             $type = $this->getType($item);
             $index = array_search($type, $groupTypes);

module/VuFindTheme/src/VuFindTheme/View/Helper/HeadLink.php

@@ -39,8 +39,10 @@ use VuFindTheme\ThemeInfo;
  * @link     https://vufind.org/wiki/development Wiki
  */
 class HeadLink extends \Zend\View\Helper\HeadLink
+    implements \Zend\Log\LoggerAwareInterface
 {
     use ConcatTrait;
+    use \VuFind\Log\LoggerAwareTrait;
 
     /**
      * Theme information service

module/VuFindTheme/src/VuFindTheme/View/Helper/HeadScript.php

@@ -39,10 +39,12 @@ use VuFindTheme\ThemeInfo;
  * @link     https://vufind.org/wiki/development Wiki
  */
 class HeadScript extends \Zend\View\Helper\HeadScript
+    implements \Zend\Log\LoggerAwareInterface
 {
     use ConcatTrait {
         getMinifiedData as getBaseMinifiedData;
     }
+    use \VuFind\Log\LoggerAwareTrait;
 
     /**
      * Theme information service