Fix some bugs with dynamic array allocation

sources/Data/Collections/ArrayList.uc

@@ -96,12 +96,15 @@ public final function ArrayList SetLength(int newLength)
 {
     local int i;
 
-    if (newLength < 0) {
-        return self;
-    }
+    if (newLength < 0)                      return self;
+    if (storedObjects.length == newLength)  return self;
+
     for (i = newLength; i < storedObjects.length; i += 1) {
         FreeItem(i);
     }
+    if (storedObjects.length <= 0) {
+        storedObjects[0] = none;
+    }
     storedObjects.length = newLength;
     return self;
 }