fix multi engine partials

features/partials.feature

@@ -37,5 +37,5 @@ Feature: Provide Sane Defaults for Partial Behavior
   Scenario: Partial and Layout use different engines
     Given the Server is running at "different-engine-partial"
     When I go to "/index.html"
-    Then I should see "ERb Main"
+    Then I should see "ERb Header"
     And I should see "Slim Footer"

fixtures/different-engine-partial/source/layouts/layout.erb

@@ -1,4 +1,7 @@
-<%= partial 'shared/erb' %>
-<%= partial 'shared/footer' %>
+<%= partial 'shared/header' %>
 
-<% yield %>
+<div id="main">
+  <%= yield %>
+</div>
+
+<%= partial 'shared/footer' %>

fixtures/different-engine-partial/source/shared/_erb.erb

@@ -1 +0,0 @@
-ERb Main

fixtures/different-engine-partial/source/shared/_header.erb

@@ -0,0 +1 @@
+<header>ERb Header</header>

lib/middleman/core_extensions/rendering.rb

@@ -39,7 +39,6 @@ module Middleman::CoreExtensions::Rendering
       engine = extension[1..-1].to_sym
 
       @current_engine, engine_was = engine, @current_engine
-      @_out_buf, _buf_was = "", @_out_buf
       
       while ::Tilt[path]
         content = render_individual_file(path, locs, opts)
@@ -56,7 +55,6 @@ module Middleman::CoreExtensions::Rendering
       content
     ensure
       @current_engine = engine_was
-      @_out_buf = _buf_was
       @content_blocks = nil
     end
     
@@ -104,6 +102,8 @@ module Middleman::CoreExtensions::Rendering
     def render_individual_file(path, locs = {}, opts = {}, &block)
       path = path.to_s
       
+      @_out_buf, _buf_was = "", @_out_buf
+      
       body = cache.fetch(:raw_template, path) do
         File.read(path)
       end
@@ -117,6 +117,8 @@ module Middleman::CoreExtensions::Rendering
       end
 
       template.render(self, locs, &block)
+    ensure  
+      @_out_buf = _buf_was
     end
     
     # @private