mag bank truncation logic

src/entity/item/mag.rs

@@ -1038,7 +1038,10 @@ impl Mag {
     }
 
     pub fn bank(&mut self) {
-        // what is the truncation logic anyway
+        self.def = self.def & 0xFFFE;
+        self.pow = self.pow & 0xFFFE;
+        self.dex = self.dex & 0xFFFE;
+        self.mind = self.mind & 0xFFFE;
     }
 
     // TODO: this needs more checks on validity