Fix nil reference in BacktraceLineDecorator (#1260)

app/decorators/backtrace_line_decorator.rb

@@ -2,7 +2,8 @@ class BacktraceLineDecorator < Draper::Decorator
   EMPTY_STRING = ''.freeze
 
   def in_app?
-    object[:file].match Backtrace::IN_APP_PATH
+    return false if file.blank?
+    file.match Backtrace::IN_APP_PATH
   end
 
   def number
@@ -14,7 +15,7 @@ def column
   end
 
   def file
-    object[:file]
+    object[:file].to_s
   end
 
   def method
@@ -40,7 +41,8 @@ def link_to_source_file(app, &block)
   end
 
   def path
-    File.dirname(object[:file]).gsub(/^\.$/, '') + "/"
+    return '' if file.blank?
+    File.dirname(file).gsub(/^\.$/, '') + "/"
   end
 
   def decorated_path

spec/decorators/backtrace_line_decorator_spec.rb

@@ -11,6 +11,9 @@
       file:   '[PROJECT_ROOT]/path/to/file/ea315ea4.rb',
       method: :instance_eval)
   end
+  let(:backtrace_line_no_file) do
+    described_class.new(number: 884, method: :instance_eval)
+  end
   let(:app) { Fabricate(:app, github_repo: 'foo/bar') }
 
   describe '#to_s' do
@@ -19,6 +22,24 @@
     end
   end
 
+  describe '#file' do
+    it 'returns "" when there is no file' do
+      expect(backtrace_line_no_file.file).to eq('')
+    end
+  end
+
+  describe '#in_app?' do
+    it 'returns false when there is no file' do
+      expect(backtrace_line_no_file.in_app?).to be false
+    end
+  end
+
+  describe '#path' do
+    it 'returns "" when there is no file' do
+      expect(backtrace_line_no_file.path).to eq ''
+    end
+  end
+
   describe '#link_to_source_file' do
     it 'adds a link to the source file' do
       link = backtrace_line_in_app.link_to_source_file(app) { 'mytext' }