Fixed PermissibleBase->clearPermissions() not unsubscribing from permissions that aren't explicitly assigned

This came to light after observing cfb6856634 in a fresh light. I noticed that this fix should not have been necessary because clearPermissions() should have dealt with it. Unfortunately, permissions can be set without being set in PermissibleBase->permissions, so this misses things.

src/pocketmine/plugin/PluginManager.php

@@ -534,6 +534,18 @@ class PluginManager{
 		}
 	}
 
+	/**
+	 * @param Permissible $permissible
+	 */
+	public function unsubscribeFromAllPermissions(Permissible $permissible) : void{
+		foreach($this->permSubs as $permission => &$subs){
+			unset($subs[spl_object_hash($permissible)]);
+			if(empty($subs)){
+				unset($this->permSubs[$permission]);
+			}
+		}
+	}
+
 	/**
 	 * @param string $permission
 	 *