[TargetIntegrator] Robustness against target with missing file references

Closes #938

lib/cocoapods/installer/user_project_integrator/target_integrator.rb

@@ -55,7 +55,9 @@ module Pod
             non_integrated = targets.reject do |target|
               target.frameworks_build_phase.files.any? do |build_file|
                 file_ref = build_file.file_ref
-                file_ref.isa == 'PBXFileReference' && file_ref.display_name == library.product_name
+                file_ref &&
+                  file_ref.isa == 'PBXFileReference' &&
+                  file_ref.display_name == library.product_name
               end
             end
             @targets = non_integrated

spec/unit/installer/user_project_integrator/target_integrator_spec.rb

@@ -45,6 +45,14 @@ module Pod
         @target_integrator.targets.map(&:name).should == %w[ SampleProject ]
       end
 
+      it 'is robust against build files with missing file references' do
+        build_file = @sample_project.new(Xcodeproj::Project::PBXBuildFile)
+        build_file.file_ref = nil
+        @target_integrator.stubs(:user_project).returns(@sample_project)
+        @target.frameworks_build_phase.files << build_file
+        @target_integrator.targets.map(&:name).should == %w[ SampleProject ]
+      end
+
       it 'does not perform the integration if there are no targets to integrate' do
         @target_integrator.stubs(:targets).returns([])
         @target_integrator.expects(:add_xcconfig_base_configuration).never