Refactor `Todo#target`

app/models/todo.rb

@@ -61,14 +61,10 @@ class Todo < ActiveRecord::Base
   # override to return commits, which are not active record
   def target
     if for_commit?
-      project.commit(commit_id)
+      project.commit(commit_id) rescue nil
     else
       super
     end
-  # Temp fix to prevent app crash
-  # if note commit id doesn't exist
-  rescue
-    nil
   end
 
   def target_reference

spec/models/todo_spec.rb

@@ -99,7 +99,8 @@ describe Todo, models: true do
   end
 
   describe '#target' do
-    it 'returns an instance of Commit for commits' do
+    context 'for commits' do
+      it 'returns an instance of Commit when exists' do
         subject.project = project
         subject.target_type = 'Commit'
         subject.commit_id = commit.id
@@ -108,6 +109,15 @@ describe Todo, models: true do
         expect(subject.target).to eq commit
       end
 
+      it 'returns nil when does not exists' do
+        subject.project = project
+        subject.target_type = 'Commit'
+        subject.commit_id = 'xxxx'
+
+        expect(subject.target).to be_nil
+      end
+    end
+
     it 'returns the issuable for issuables' do
       subject.target_id = issue.id
       subject.target_type = issue.class.name