font size cannot be null

model/src/main/java/lcsb/mapviewer/model/map/species/Element.java

@@ -140,6 +140,7 @@ public abstract class Element implements BioEntity, Serializable, SbmlArgument {
   /**
    * Size of the font used for description.
    */
+  @Column(nullable = false)
   private Double fontSize;
 
   /**

persist/src/main/resources/db/migration/15.0.0/V15.0.1.20191025__font_size.sql

+update element_table set font_size = 12 where font_size is null;
+alter table element_table alter column font_size set not null;