Only booleans are allowed in an if condition

Author: sasezaki

src/Rules/PlaceholderCharactersRule.php

@@ -86,13 +86,13 @@ public function processNode(Node $node, Scope $scope): array
             $message = $constantStringType->getValue();
 
             $doubleBraceError = self::checkDoubleBrace($message, $methodName);
-            if ($doubleBraceError) {
+            if ($doubleBraceError instanceof RuleError) {
                 $errors[] = $doubleBraceError;
                 continue;
             }
 
             $invalidCharError = self::checkInvalidChar($message, $methodName);
-            if ($invalidCharError) {
+            if ($invalidCharError instanceof RuleError) {
                 $errors[] = $invalidCharError;
             }
         }

src/Rules/PlaceholderCorrespondToKeysRule.php

@@ -99,7 +99,7 @@ public function processNode(Node $node, Scope $scope): array
             $context = $args[$contextArgumentNo];
 
             $doesNohHaveError = self::contextDoesNotHavePlaceholderKey($scope->getType($context->value), $methodName, $matches[0], $matches[1]);
-            if ($doesNohHaveError) {
+            if ($doesNohHaveError instanceof RuleError) {
                 $errors[] = $doesNohHaveError;
             }
         }