fix on accesibility of big files

annotation/src/main/java/lcsb/mapviewer/annotation/cache/BigFileCache.java

@@ -815,8 +815,7 @@ public class BigFileCache {
 			File f = new File(Configuration.getWebAppDir() + entry.getLocalPath());
 			if (!f.exists()) {
 				logger.warn("File is supposed to be cached but it's not there... " + sourceUrl);
-				bigFileEntryDao.delete(entry);
-				entry = null;
+				return false;
 			}
 		}
 		return entry != null;