Fix 10 PHPStan errors

src/Core/Storage/Type/Database.php

@@ -80,7 +80,7 @@ class Database implements ICanWriteToStorage
 				throw new StorageException(sprintf('Database storage failed to update %s', $reference), 500, new Exception($this->dba->errorMessage(), $this->dba->errorNo()));
 			}
 
-			return $this->dba->lastInsertId();
+			return (string) $this->dba->lastInsertId();
 		}
 	}
 

src/Core/System.php

@@ -452,19 +452,17 @@ class System
 
 	/**
 	 * Returns the current Load of the System
-	 *
-	 * @return integer
 	 */
-	public static function currentLoad()
+	public static function currentLoad(): float
 	{
 		if (!function_exists('sys_getloadavg')) {
-			return false;
+			return (float) 0;
 		}
 
 		$load_arr = sys_getloadavg();
 
 		if (!is_array($load_arr)) {
-			return false;
+			return (float) 0;
 		}
 
 		return round(max($load_arr[0], $load_arr[1]), 2);

src/Core/Update.php

@@ -217,7 +217,7 @@ class Update
 										->set('system', 'maintenance', false)
 										->delete('system', 'maintenance_reason')
 										->commit();
-							return $r;
+							return 'Pre update failed';
 						} else {
 							DI::logger()->notice('Pre update executed.', ['version' => $version]);
 						}
@@ -262,7 +262,7 @@ class Update
 										->set('system', 'maintenance', false)
 										->delete('system', 'maintenance_reason')
 										->commit();
-							return $r;
+							return 'Post update failed';
 						} else {
 							DI::config()->set('system', 'build', $version);
 							DI::logger()->notice('Post update executed.', ['version' => $version]);

src/Core/Worker.php

@@ -271,12 +271,13 @@ class Worker
 	 *
 	 * @param integer $priority The priority that should be checked
 	 *
-	 * @return integer Is there a process running with that priority?
+	 * @return bool Is there a process running with that priority?
 	 * @throws \Exception
 	 */
-	private static function processWithPriorityActive(int $priority): int
+	private static function processWithPriorityActive(int $priority): bool
 	{
 		$condition = ["`priority` <= ? AND `pid` != 0 AND NOT `done`", $priority];
+
 		return DBA::exists('workerqueue', $condition);
 	}
 
@@ -955,7 +956,7 @@ class Worker
 	/**
 	 * Returns the priority of the next workerqueue job
 	 *
-	 * @return string|bool priority or FALSE on failure
+	 * @return int|false priority or FALSE on failure
 	 * @throws \Exception
 	 */
 	private static function nextPriority()