don't fetch glyph content if glyph does not exist

model/src/main/java/lcsb/mapviewer/model/map/layout/graphics/Glyph.java

@@ -69,8 +69,10 @@ public class Glyph implements Serializable {
   public Glyph(Glyph original) {
     // we should reference to the same file
     setFile(original.getFile());
-    //make sure that the content is available
-    original.getFile().getFileContent();
+    if (original.getFile() != null) {
+      // make sure that the content is available
+      original.getFile().getFileContent();
+    }
   }
 
   public UploadedFileEntry getFile() {