Fix: allow_blank false for Time attributes with valid values causes NoMethodError.

Author: ipkes

CHANGELOG.md

@@ -10,6 +10,7 @@
 #### Fixes
 
 * [#1365](https://github.com/ruby-grape/grape/pull/1365): Fix finding exception handler in error middleware - [@ktimothy](https://github.com/ktimothy).
+* [#1380](https://github.com/ruby-grape/grape/pull/1380): Fix `allow_blank: false` for `Time` attributes with valid values causes `NoMethodError` - [@ipkes](https://github.com/ipkes).
 
 0.16.2 (4/12/2016)
 ==================

lib/grape/validations/validators/allow_blank.rb

@@ -20,7 +20,7 @@ def validate_param!(attr_name, params)
 
         return unless should_validate
 
-        return if value == false || value.present?
+        return if false == value || value.present?
 
         raise Grape::Exceptions::Validation, params: [@scope.full_name(attr_name)], message: message(:blank)
       end

spec/grape/validations/validators/allow_blank_spec.rb

@@ -488,6 +488,11 @@ def app
       get '/disallow_boolean_blank', val: false
       expect(last_response.status).to eq(200)
     end
+
+    it 'accepts value when time allow_blank' do
+      get '/disallow_datetime_blank', val: Time.now
+      expect(last_response.status).to eq(200)
+    end
   end
 
   context 'in an optional group' do