Make checks for continue_params more robust

The check for continue_params&.key?(:to) in Projects::ImportsController
caused an exception in redirect_to if this key contained a nil value.

Since url_for won't add any params for an empty hash, we can just return
that in continue_params if params[:continue] isn't present, and simplify
the code in the controllers to check for the values we actually want to
use.

app/controllers/concerns/continue_params.rb

@@ -6,7 +6,7 @@ module ContinueParams
 
   def continue_params
     continue_params = params[:continue]
-    return unless continue_params
+    return {} unless continue_params
 
     continue_params = continue_params.permit(:to, :notice, :notice_now)
     continue_params[:to] = safe_redirect_path(continue_params[:to])

app/controllers/projects/forks_controller.rb

@@ -46,20 +46,16 @@ class Projects::ForksController < Projects::ApplicationController
 
     @forked_project ||= ::Projects::ForkService.new(project, current_user, namespace: namespace).execute
 
-    if @forked_project.saved? && @forked_project.forked?
-      if @forked_project.import_in_progress?
+    if !@forked_project.saved? || !@forked_project.forked?
+      render :error
+    elsif @forked_project.import_in_progress?
       redirect_to project_import_path(@forked_project, continue: continue_params)
-      else
-        if continue_params
+    elsif continue_params[:to]
       redirect_to continue_params[:to], notice: continue_params[:notice]
     else
       redirect_to project_path(@forked_project), notice: "The project '#{@forked_project.name}' was successfully forked."
     end
   end
-    else
-      render :error
-    end
-  end
   # rubocop: enable CodeReuse/ActiveRecord
 
   def whitelist_query_limiting

app/controllers/projects/imports_controller.rb

@@ -23,7 +23,7 @@ class Projects::ImportsController < Projects::ApplicationController
 
   def show
     if @project.import_finished?
-      if continue_params&.key?(:to)
+      if continue_params[:to]
         redirect_to continue_params[:to], notice: continue_params[:notice]
       else
         redirect_to project_path(@project), notice: finished_notice
@@ -31,12 +31,8 @@ class Projects::ImportsController < Projects::ApplicationController
     elsif @project.import_failed?
       redirect_to new_project_import_path(@project)
     else
-      if continue_params && continue_params[:notice_now]
       flash.now[:notice] = continue_params[:notice_now]
     end
-
-      # Render
-    end
   end
 
   private

app/controllers/projects/jobs_controller.rb

@@ -103,7 +103,7 @@ class Projects::JobsController < Projects::ApplicationController
 
     @build.cancel
 
-    if continue_params
+    if continue_params[:to]
       redirect_to continue_params[:to]
     else
       redirect_to builds_project_pipeline_path(@project, @build.pipeline.id)

spec/controllers/concerns/continue_params_spec.rb

@@ -18,6 +18,14 @@ describe ContinueParams do
     ActionController::Parameters.new(continue: params)
   end
 
+  it 'returns an empty hash if params are not present' do
+    allow(controller).to receive(:params) do
+      ActionController::Parameters.new
+    end
+
+    expect(controller.continue_params).to eq({})
+  end
+
   it 'cleans up any params that are not allowed' do
     allow(controller).to receive(:params) do
       strong_continue_params(to: '/hello',