Fix issues detected by psalm

Author: discordier

src/JsonRepositoryWriter.php

@@ -19,7 +19,7 @@
  */
 class JsonRepositoryWriter
 {
-    private const JSON_FLAGS = JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE;
+    private const int JSON_FLAGS = JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE;
 
     private string $baseDir;
 
@@ -144,7 +144,7 @@ private function processTool(ToolInterface $tool): ?array
             }
             $data['tools'][$name][] = $serialized;
         }
-        if (empty($data['tools'])) {
+        if (!(bool) $data['tools']) {
             return null;
         }
 

src/SourceProvider/Tool/ToolVersionFilter.php

@@ -9,8 +9,8 @@
 
 final class ToolVersionFilter
 {
-    public const WILDCARD_CONSTRAINT = '*';
-    public const NEVER_MATCHING_CONSTRAINT = '>0 <0';
+    public const string WILDCARD_CONSTRAINT = '*';
+    public const string NEVER_MATCHING_CONSTRAINT = '>0 <0';
 
     private string $toolName;
     private string $allowedVersions;