Fix: Add null-handling for poolSize property

CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/database/DatabaseSettings.java

@@ -51,19 +51,19 @@ public final class DatabaseSettings {
         boolean attemptFallback = attemptFallbackString == null || Boolean.parseBoolean(attemptFallbackString);
         boolean debugMode = Boolean.parseBoolean(debugModeString);
         boolean tempMode = Boolean.parseBoolean(tempModeString);
-        int poolSize;
+
+        int poolSize = defaultConfig.connectionPoolSize();
+        if (poolSizeString != null && !poolSizeString.isBlank()){
             try {
-             poolSize = Integer.parseInt(poolSizeString);
-             if (poolSize < 1) {
-                 //TODO: Localize String
-                 logger.warn("poolSize property cannot be less than 1, using default value");
-                 poolSize = defaultConfig.connectionPoolSize();
-             }
+                int size = Integer.parseInt(poolSizeString);
+                if (size < 1) {
+                    logger.warn(Localization.getText("DatabaseSettings.poolSizeLessThanOne"));
+                } else poolSize = size;
             } catch (NumberFormatException e) {
-            //TODO: Localize String
-            logger.warn("poolSize property must be an integer, using default value");
-            poolSize = defaultConfig.connectionPoolSize();
+                logger.warn(Localization.getText("DatabaseSettings.poolSizeNaN"));
             }
+        }
+
 
         if (name == null || name.isBlank()){
             name = defaultConfig.databaseName();