recover gradefully from empty render method

lib/ruby2js/filter/react.rb

@@ -94,7 +94,7 @@ def on_class(node)
               end
 
             elsif mname == :render
-              if block.length != 1 or block.last.type == :begin
+              if block.length!=1 or not block.last or block.last.type==:begin
                 # wrap multi-line blocks with a 'div' element
                 block = [s(:return, 
                   s(:block, s(:send, nil, :_div), s(:args), *block))]

spec/react_spec.rb

@@ -126,6 +126,16 @@ def to_js(string)
       result.must_include ', React.createElement("h1", null, "a"),'
       result.must_include ', React.createElement("p", null, "b"))}})'
     end
+
+    it "should insert a div if no elements are present" do
+      result = to_js( 'class Foo<React; def render; end; end' )
+      result.must_include 'return React.createElement("div")'
+    end
+
+    it "should insert a div if method is empty" do
+      result = to_js( 'class Foo<React; def render; end; end' )
+      result.must_include 'return React.createElement("div")'
+    end
   end
 
   describe "class attributes" do