Undefined in Config::set always unsets the value

spec/config-spec.coffee

@@ -577,6 +577,23 @@ describe "Config", ->
         atom.config.set('foo.bar.anInt', 'cats')
         expect(atom.config.get('foo.bar.anInt')).toBe 'cats'
 
+    describe 'when the value has an "string" and "boolean" type', ->
+      beforeEach ->
+        schema =
+          type: ['string', 'boolean']
+          default: 'def'
+        atom.config.setSchema('foo.bar', schema)
+
+      it 'can set a string, a boolean, and unset', ->
+        atom.config.set('foo.bar', 'ok')
+        expect(atom.config.get('foo.bar')).toBe 'ok'
+
+        atom.config.set('foo.bar', false)
+        expect(atom.config.get('foo.bar')).toBe false
+
+        atom.config.set('foo.bar', undefined)
+        expect(atom.config.get('foo.bar')).toBe 'def'
+
     describe 'when the value has a "number" type', ->
       beforeEach ->
         schema =

src/config.coffee

@@ -381,10 +381,11 @@ class Config
   # * `true` if the value was set.
   # * `false` if the value was not able to be coerced to the type specified in the setting's schema.
   set: (keyPath, value) ->
-    try
-      value = @scrubValue(keyPath, value)
-    catch e
-      return false
+    unless value == undefined
+      try
+        value = @scrubValue(keyPath, value)
+      catch e
+        return false
 
     if @get(keyPath) isnt value
       defaultValue = _.valueForKeyPath(@defaultSettings, keyPath)