Write null when ReadI fails to prevent confusion

Author: Anuken

core/src/mindustry/logic/LExecutor.java

@@ -619,12 +619,17 @@ public ReadI(){
         public void run(LExecutor exec){
             Object targetObj = target.obj();
             if(targetObj instanceof LReadable read){
-                if(!read.readable(exec)) return;
+                if(!read.readable(exec)){
+                    output.setobj(null);
+                    return;
+                }
                 read.read(position, output);
             }else{
                 int address = position.numi();
                 if(targetObj instanceof CharSequence str){
                     output.setnum(address < 0 || address >= str.length() ? Double.NaN : (int)str.charAt(address));
+                }else{
+                    output.setobj(null);
                 }
             }
         }