Fix trainer wizard crash on step 6 — skip validate() when rules are empty

Livewire's validate([]) falls back to looking for a $rules property on
the component. Steps 6 and 7 intentionally have no validation rules, so
only call validate() when the rules array is non-empty.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Livewire/HR/CreateTrainerWizard.php

@@ -346,10 +346,11 @@ public function messagesForStep(int $step): array
 
     public function nextStep(): void
     {
-        $this->validate(
-            $this->rulesForStep($this->currentStep),
-            $this->messagesForStep($this->currentStep)
-        );
+        $rules = $this->rulesForStep($this->currentStep);
+
+        if (!empty($rules)) {
+            $this->validate($rules, $this->messagesForStep($this->currentStep));
+        }
 
         if ($this->currentStep < $this->totalSteps) {
             $this->currentStep++;