Fix empty statement fields shifting the remaining parameters (#12715)

* Fix empty statement fields shifting remaining parameters

* Fixed unit tests

core/src/mindustry/logic/LStatement.java

@@ -90,7 +90,7 @@ public abstract class LStatement{
     /** Sanitizes variable input strings from text fields into values that will not break logic parsing. */
     public static String sanitize(String value){
         if(value.length() == 0){
-            return "";
+            return "null";
         }else if(value.length() == 1){
             if(value.charAt(0) == '"' || value.charAt(0) == ';' || value.charAt(0) == ' ' ||
             value.charAt(0) == '\n' || value.charAt(0) == '\t' || value.charAt(0) == '#'){

tests/src/test/java/LogicTests.java

@@ -123,7 +123,7 @@ public class LogicTests{
         Arguments.of("a bare single semicolon is invalid", ";", "invalid"),
         Arguments.of("a bare single space is invalid", " ", "invalid"),
         Arguments.of("a single ordinary character passes through unchanged", "a", "a"),
-        Arguments.of("empty input stays empty", "", ""),
+        Arguments.of("empty input gets converted to null", "", "null"),
         Arguments.of("a plain already-quoted value is untouched", "\"hello\"", "\"hello\""),
         Arguments.of("a unescaped quote at the end gets doubled", "\"hello\\\"", "\"hello\\\\\""),
         Arguments.of(
@@ -454,4 +454,4 @@ public class LogicTests{
     void crlfLabelsResolveToTheSameJumpLocationAsLfLabels(){
         assertDoesNotThrow(() -> load("loop:\r\njump loop always\r\n"));
     }
-}
+}