chore: rector fixes

src/Plugins/Shard.php

@@ -234,9 +234,7 @@ private function buildFilterArgument(array $testsToRun): string
             $parts = explode('\\', $class);
             $current = &$tree;
             foreach ($parts as $part) {
-                if (! isset($current[$part])) {
-                    $current[$part] = [];
-                }
+                $current[$part] ??= [];
                 $current = &$current[$part];
             }
         }

src/Plugins/Tia.php

@@ -1537,9 +1537,7 @@ private function consumePartials(array $partialKeys): array
 
             foreach (['files', 'tables', 'inertia'] as $section) {
                 foreach ($data[$section] as $testFile => $values) {
-                    if (! isset($merged[$section][$testFile])) {
-                        $merged[$section][$testFile] = [];
-                    }
+                    $merged[$section][$testFile] ??= [];
 
                     foreach ($values as $value) {
                         $merged[$section][$testFile][$value] = true;

src/Plugins/Tia/Graph.php

@@ -1020,9 +1020,7 @@ private function withoutFilesCoveredBy(array $results, array $authoritative): ar
 
     private function ensureBaseline(string $branch): void
     {
-        if (! isset($this->baselines[$branch])) {
-            $this->baselines[$branch] = ['sha' => null, 'tree' => [], 'results' => []];
-        }
+        $this->baselines[$branch] ??= ['sha' => null, 'tree' => [], 'results' => []];
     }
 
     /**
@@ -1067,9 +1065,7 @@ public function markKnownTestFiles(array $testFiles): void
                 continue;
             }
 
-            if (! isset($this->edges[$rel])) {
-                $this->edges[$rel] = [];
-            }
+            $this->edges[$rel] ??= [];
         }
     }
 

src/Preset.php

@@ -111,9 +111,7 @@ private function executePreset(AbstractPreset $preset): AbstractPreset
      */
     private function baseNamespaces(): array
     {
-        if (self::$baseNamespaces === null) {
-            self::$baseNamespaces = Composer::userNamespaces();
-        }
+        self::$baseNamespaces ??= Composer::userNamespaces();
 
         return self::$baseNamespaces;
     }