Handle missing settings table for metrics

This ensures we can still boot, even when the "application_settings"
table doesn't exist.

lib/gitlab/metrics.rb

@@ -9,13 +9,17 @@ module Gitlab
     # etc). This ensures the application is able to boot up even when the
     # migrations have not been executed.
     def self.settings
-      ApplicationSetting.current || {
+      if ApplicationSetting.table_exists? and curr = ApplicationSetting.current
+        curr
+      else
+        {
           metrics_pool_size:             16,
           metrics_timeout:               10,
           metrics_enabled:               false,
           metrics_method_call_threshold: 10
         }
       end
+    end
 
     def self.pool_size
       settings[:metrics_pool_size]

spec/lib/gitlab/metrics_spec.rb

@@ -29,7 +29,7 @@ describe Gitlab::Metrics do
     it 'returns an Array containing a file path and line number' do
       file, line = described_class.last_relative_application_frame
 
-      expect(line).to eq(30)
+      expect(line).to eq(__LINE__ - 2)
       expect(file).to eq('spec/lib/gitlab/metrics_spec.rb')
     end
   end