Fixed submit button not enabling

Fixed tests

app/assets/javascripts/gl_dropdown.js.coffee

@@ -518,7 +518,9 @@ class GitLabDropdown
         if !field.length and fieldName
           @addInput(fieldName, value)
         else
-          field.val value
+          field
+            .val value
+            .trigger 'change'
 
       return selectedObject
 

spec/features/compare_spec.rb

@@ -16,7 +16,7 @@ describe "Compare", js: true do
     end
 
     it "should compare branches" do
-      fill_in "from", with: "mast"
+      fill_in "from", with: "fea"
       find("#from").click
 
       click_link "feature"