Network page appear with an error message when entering nonexistent git revision

app/assets/javascripts/network/network_bundle.js

@@ -9,6 +9,8 @@
 
 (function() {
   $(function() {
+    if (!$(".network-graph").length) return;
+
     var network_graph;
     network_graph = new Network({
       url: $(".network-graph").attr('data-url'),

app/controllers/projects/network_controller.rb

@@ -11,7 +11,9 @@ class Projects::NetworkController < Projects::ApplicationController
     @commit_url = namespace_project_commit_path(@project.namespace, @project, 'ae45ca32').gsub("ae45ca32", "%s")
 
     respond_to do |format|
-      format.html
+      format.html do
+        flash.now[:alert] = "Git revision '#{params[:extended_sha1]}' does not exist." if params[:extended_sha1].present? && !@commit
+      end
 
       format.json do
         @graph = Network::Graph.new(project, @ref, @commit, @options[:filter_ref])

app/views/projects/network/show.html.haml

@@ -17,5 +17,6 @@
               = check_box_tag :filter_ref, 1, @options[:filter_ref]
               %span Begin with the selected commit
 
-    .network-graph{ data: { url: @url, commit_url: @commit_url, ref: @ref, commit_id: @commit.id } }
-      = spinner nil, true
+    - if @commit
+      .network-graph{ data: { url: @url, commit_url: @commit_url, ref: @ref, commit_id: @commit.id } }
+        = spinner nil, true

lib/extracts_path.rb

@@ -125,9 +125,9 @@ module ExtractsPath
 
         request.format = :atom if @commit
       end
-    end
 
-    raise InvalidPathError unless @commit
+      raise InvalidPathError unless @commit
+    end
 
     @hex_path = Digest::SHA1.hexdigest(@path)
     @logs_path = logs_file_namespace_project_ref_path(@project.namespace,