Fix column suggestions for empty custom vars of type array

library/Icingadb/Web/Control/SearchBar/ObjectSuggestions.php

@@ -214,13 +214,11 @@ protected function fetchColumnSuggestions($searchTerm)
         $titleAdded = false;
         foreach ($this->getDb()->select($this->queryCustomvarConfig($searchTerm)) as $customVar) {
             $search = $name = $customVar->flatname;
-            if (preg_match('/\w+\[(\d+)]$/', $search, $matches)) {
-                // array vars need to be specifically handled
-                if ($matches[1] !== '0') {
-                    continue;
-                }
-
-                $name = substr($search, 0, -3);
+            if (preg_match('/\w+\[(\d*)]$/', $search, $matches)) {
+                // Count the digits of the used array index and add the len of the curly brackets (2). The hardcoded
+                // previously used value `-3` may fail for array indices `>= 10`.
+                $length = $matches[1] === "" ? 2 : (int) log10((int) $matches[1]) + 1 + 2;
+                $name = substr($search, 0, -$length);
                 $search = $name . '[*]';
             }