Crash fix

core/src/mindustry/entities/Units.java

@@ -214,7 +214,10 @@ public class Units{
             }
         });
 
-        return buildResult;
+        var result = buildResult;
+        buildResult = null;
+
+        return result;
     }
 
     /** Iterates through all buildings in a range. */

core/src/mindustry/entities/comp/PlayerComp.java

@@ -183,7 +183,9 @@ abstract class PlayerComp implements UnitController, Entityc, Syncc, Timerc, Dra
         if(!unit.isNull()){
             clearUnit();
         }
-        lastReadUnit = justSwitchTo = justSwitchFrom = null;
+
+        lastReadUnit = Nulls.unit;
+        justSwitchTo = justSwitchFrom = null;
     }
 
     public void team(Team team){