qml: check passphrase not empty when checked

electrum/gui/qml/components/wizard/WCCreateSeed.qml

@@ -9,7 +9,7 @@ import "../controls"
 WizardComponent {
     securePage: true
 
-    valid: seedtext.text != ''
+    valid: seedtext.text != '' && extendcb.checked ? customwordstext.text != '' : true
 
     function apply() {
         wizard_data['seed'] = seedtext.text

electrum/gui/qml/components/wizard/WCHaveSeed.qml

@@ -68,6 +68,9 @@ WizardComponent {
         valid = false
         validationtext.text = ''
 
+        if (extendcb.checked && customwordstext.text == '')
+            return
+
         var validSeed = bitcoin.verifySeed(seedtext.text, seed_variant_cb.currentValue, wizard_data['wallet_type'])
         if (!cosigner || !validSeed) {
             valid = validSeed