fix: Map key comparison, preventing NPE

src/main/java/eu/ztsh/lfr/core/impl/TemperaturesServiceImpl.java

@@ -30,7 +30,7 @@ public class TemperaturesServiceImpl implements TemperaturesService {
                 Thread.currentThread().interrupt();
             }
         }
-        return averages.get().get(city);
+        return averages.get().getOrDefault(city.toLowerCase(), List.of());
     }
 
     @EventListener(FileProcessedEvent.class)

src/main/java/eu/ztsh/lfr/core/impl/files/FileLoadingService.java

@@ -79,7 +79,9 @@ public class FileLoadingService {
                 .map(line -> {
                     try {
                         var parts = line.split(";");
-                        return new DataRow(parts[0], Integer.parseInt(parts[1].split("-")[0]), Double.parseDouble(parts[2]));
+                        return new DataRow(parts[0].toLowerCase(),
+                            Integer.parseInt(parts[1].split("-")[0]),
+                            Double.parseDouble(parts[2]));
                     } catch (Exception e) {
                         throw new FileProcessingException("Error in line %s".formatted(line), e);
                     }