Cron: Remove errant false values in cron array when upgrading to 5.9+.

[51916] fixed a bug where `array( `false` )` was added to the cron array when `_get_cron_array()` returned `false`. 

This commit:
* Removes any `false` values from the cron array when upgrading to 5.9+.
* Bumps the database version.

Follow-up to [44917], [51916].

Props peterwilsoncc, jrf.
See #53950.

git-svn-id: https://develop.svn.wordpress.org/trunk@51917 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/upgrade.php

@@ -832,6 +832,10 @@ function upgrade_all() {
 		upgrade_560();
 	}
 
+	if ( $wp_current_db_version < 51917 ) {
+		upgrade_590();
+	}
+
 	maybe_disable_link_manager();
 
 	maybe_disable_automattic_widgets();
@@ -2248,6 +2252,23 @@ function upgrade_560() {
 	}
 }
 
+/**
+ * Executes changes made in WordPress 5.9.0.
+ *
+ * @ignore
+ * @since 5.9.0
+ */
+function upgrade_590() {
+	global $wp_current_db_version;
+
+	if ( $wp_current_db_version < 51917 ) {
+		$crons = _get_cron_array();
+		// Remove errant `false` values, see #53950.
+		$crons = array_filter( $crons );
+		_set_cron_array( $crons );
+	}
+}
+
 /**
  * Executes network-level upgrade routines.
  *

src/wp-includes/version.php

@@ -23,7 +23,7 @@
  *
  * @global int $wp_db_version
  */
-$wp_db_version = 49752;
+$wp_db_version = 51917;
 
 /**
  * Holds the TinyMCE version.