Allow search specs caching to be disabled without fatal error.

module/VuFind/src/VuFind/Config/SearchSpecsReader.php

@@ -75,8 +75,13 @@ class SearchSpecsReader
         // Load data if it is not already in the object's cache:
         if (!isset($this->searchSpecs[$filename])) {
             // Connect to searchspecs cache:
-            $cache = (null !== $this->cacheManager)
-                ? $this->cacheManager->getCache('searchspecs') : false;
+            try {
+                $cache = (null !== $this->cacheManager)
+                    ? $this->cacheManager->getCache('searchspecs') : false;
+            } catch (\Exception $e) {
+                // Don't blow up if we fail to retrieve the desired cache:
+                $cache = false;
+            }
 
             // Determine full configuration file path:
             $fullpath = Locator::getBaseConfigPath($filename);