Resolve "Image Export Error"

Closes #1130 (closed)

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

@@ -69,6 +69,8 @@ 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();
   }
 
   public UploadedFileEntry getFile() {