Explicit error when commit not found in the GitLab CI

app/assets/javascripts/merge_request_widget.js.coffee

@@ -36,11 +36,11 @@ class @MergeRequestWidget
 
   showCiState: (state) ->
     $('.ci_widget').hide()
-    allowed_states = ["failed", "canceled", "running", "pending", "success"]
+    allowed_states = ["failed", "canceled", "running", "pending", "success", "not_found"]
     if state in allowed_states
       $('.ci_widget.ci-' + state).show()
       switch state
-        when "failed", "canceled"
+        when "failed", "canceled", "not_found"
           @setMergeButtonClass('btn-danger')
         when "running", "pending"
           @setMergeButtonClass('btn-warning')

app/views/projects/merge_requests/widget/_heading.html.haml

@@ -23,6 +23,12 @@
       = icon("spinner spin")
       Checking for CI status for #{@merge_request.last_commit_short_sha}
 
+    .ci_widget.ci-not_found{style: "display:none"}
+      = icon("times")
+      %span Can not find commit in the CI server
+      for #{@merge_request.last_commit_short_sha}.
+      
+
     .ci_widget.ci-canceled{style: "display:none"}
       = icon("times")
       %span CI build canceled