[NEWS] Document WeakRef to raise with unsupported classes.

NEWS

@@ -1,5 +1,8 @@
 = RubyMotion 2.25 =
 
+  * Improved use of `WeakRef' to raise an exception when trying to create a
+    weak reference to one of the unsupported classes. For more information, see
+    `Which classes don’t support weak references?' at http://bit.ly/1iiSOaU.
   * Fixed a bug where KVC property validation methods defined in Ruby would not
     be compiled with the appropriate (Pointer) types.
   * Added some introspection support to `ImmediateRef'. It can now report the

test/test/spec/weakref_spec.rb

@@ -107,6 +107,11 @@ describe "WeakRef" do
     WeakRef.new(true).should == true
     WeakRef.new(false).should == false
   end
+
+  it "raises with classes that do not support weak references" do
+    obj = NSMutableParagraphStyle.new
+    lambda { WeakRef.new(obj) }.should.raise(WeakRef::RefError)
+  end
 end
 
 describe "Proc#weak!" do