Issue #2811519 by tim.plunkett, dbourrion, cilefen, futurmat: Blocks do not appear after being placed with the Rules module enabled (or other missing schemata for Condition plugins)

core/modules/block/src/BlockForm.php

@@ -323,7 +323,7 @@ class BlockForm extends EntityForm {
       // However, certain form elements may return it as 0/1. Cast here to
       // ensure the data is in the expected type.
       if (array_key_exists('negate', $values)) {
-        $values['negate'] = (bool) $values['negate'];
+        $form_state->setValue(['visibility', $condition_id, 'negate'], (bool) $values['negate']);
       }
 
       // Allow the condition to validate the form.

core/modules/block/tests/modules/block_test/src/Plugin/Condition/MissingSchema.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Drupal\block_test\Plugin\Condition;
+
+use Drupal\Core\Condition\ConditionPluginBase;
+
+/**
+ * Provides a 'missing_schema' condition.
+ *
+ * @Condition(
+ *   id = "missing_schema",
+ *   label = @Translation("Missing schema"),
+ * )
+ */
+class MissingSchema extends ConditionPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function evaluate() {
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function summary() {
+    return 'Summary';
+  }
+
+}