Make custom Env flag reliably possible (#8019)

* Make custom Env flag reliably possible

* screw you

* "compatibility" for mods that don't use add()

tests/src/test/java/ApplicationTests.java

@@ -190,7 +190,7 @@ public class ApplicationTests{
 
     @Test
     void writeRules(){
-        ByteBuffer buffer = ByteBuffer.allocate(500);
+        ByteBuffer buffer = ByteBuffer.allocate(1000);
 
         Rules rules = new Rules();
         rules.attackMode = true;
@@ -981,4 +981,4 @@ public class ApplicationTests{
         tile.build.handleStack(item, 1, unit);
         assertEquals(capacity, tile.build.items.get(item));
     }
-}
+}