diff --git a/application/libraries/FehlerUpdateLib.php b/application/libraries/FehlerUpdateLib.php
index a969bffba..5eca64f76 100644
--- a/application/libraries/FehlerUpdateLib.php
+++ b/application/libraries/FehlerUpdateLib.php
@@ -59,8 +59,9 @@ class FehlerUpdateLib
 		// Loads EPrintfLib
 		$this->_ci->load->library('EPrintfLib');
 
-		// Loads the PhraseModel
+		// Loads the Models
 		$this->_ci->load->model('system/Fehler_model', 'FehlerModel');
+		$this->_ci->load->model('system/App_model', 'AppModel');
 	}
 
 	// -----------------------------------------------------------------------------------------------------------------
@@ -93,7 +94,6 @@ class FehlerUpdateLib
 				$this->installFrom($configFilePath);
 			}
 		}
-
 	}
 
 	/**
@@ -207,23 +207,23 @@ class FehlerUpdateLib
 
 		// no fehler has been found
 
-		// hanlde apps
+		// handle apps
 		if (isset($fehler[self::APP]))
 		{
 			$apps = $fehler[self::APP];
 			if (is_string($apps)) $apps = [$apps];
-			//unset($fehler[self::APP]);
+
+			foreach ($apps as $app)
+			{
+				// check if app exists in db
+				$this->_ci->AppModel->addSelect('1');
+				$appRes = $this->_ci->AppModel->loadWhere(['app' => $app]);
+
+				if (!hasData($appRes)) return error("App ".$app." does not exist");
+				// TODO add entry for each app
+			}
+
 			$fehler[self::APP] = $apps[0];
-
-			//~ foreach ($apps as $app)
-			//~ {
-				//~ // TODO add entry for each app
-				//~ foreach ($_ as $_)
-				//~ {
-
-				//~ }
-
-			//~ }
 		}
 
 		// Then add the fehler to the database
diff --git a/application/libraries/issues/PlausicheckProducerLib.php b/application/libraries/issues/PlausicheckProducerLib.php
index 0cd76962a..34807c917 100644
--- a/application/libraries/issues/PlausicheckProducerLib.php
+++ b/application/libraries/issues/PlausicheckProducerLib.php
@@ -144,6 +144,7 @@ class PlausicheckProducerLib
 		$result = new StdClass();
 		$result->errors = [];
 		$result->infos = [];
+
 		$mappingFehlerKurbz = array_keys($this->_fehlerLibMappings);
 
 		// check if all issues to produce could be found in database
diff --git a/application/libraries/issues/PlausicheckResolverLib.php b/application/libraries/issues/PlausicheckResolverLib.php
index 89b68a7b8..06c3705a3 100644
--- a/application/libraries/issues/PlausicheckResolverLib.php
+++ b/application/libraries/issues/PlausicheckResolverLib.php
@@ -161,7 +161,7 @@ class PlausicheckResolverLib
 			if (isset($this->_codeLibMappings[$issue->fehlercode]))
 			{
 				$codeLibMapping = $this->_codeLibMappings[$issue->fehlercode];
-				$libName = $codeLibMapping[self::RESOLVER_LIB_NAME];
+				$libName = $codeLibMapping[self::RESOLVER_LIB_NAME] ?? null;
 				$extensionName = $codeLibMapping[self::EXTENSION_NAME] ?? null;
 				$producerIsResolver = $codeLibMapping[self::PRODUCER_IS_RESOLVER_NAME] ?? false;
 
diff --git a/application/models/system/App_model.php b/application/models/system/App_model.php
new file mode 100644
index 000000000..85d015f42
--- /dev/null
+++ b/application/models/system/App_model.php
@@ -0,0 +1,14 @@
+<?php
+class App_model extends DB_Model
+{
+
+	/**
+	 * Constructor
+	 */
+	public function __construct()
+	{
+		parent::__construct();
+		$this->dbTable = 'system.tbl_app';
+		$this->pk = 'app';
+	}
+}