Validate conditions when making a query.

Author: timgws

src/QueryBuilderParser/QBPFunctions.php

@@ -95,6 +95,10 @@ protected function operatorIsNull($operator)
      */
     protected function validateCondition($condition)
     {
+        if (is_null($condition)) {
+            return $condition;
+        }
+
         $condition = trim(strtolower($condition));
 
         if ($condition !== 'and' && $condition !== 'or') {

src/QueryBuilderParser/QueryBuilderParser.php

@@ -216,6 +216,7 @@ protected function makeQuery(Builder $query, stdClass $rule, $queryCondition = '
         /*
          * Ensure that the value is correct for the rule, return query on exception
          */
+        $this->validateCondition($queryCondition);
         try {
             $value = $this->getValueForQueryFromRule($rule);
         } catch (QBRuleException $e) {