Ensure branches Hash is present when supported

Author: marcotc

lib/simplecov/combine/files_combiner.rb

@@ -16,7 +16,7 @@ module FilesCombiner
       #
       def combine(coverage_a, coverage_b)
         combination = {"lines" => Combine.combine(LinesCombiner, coverage_a["lines"], coverage_b["lines"])}
-        combination["branches"] = Combine.combine(BranchesCombiner, coverage_a["branches"], coverage_b["branches"]) if SimpleCov.branch_coverage?
+        combination["branches"] = Combine.combine(BranchesCombiner, coverage_a["branches"], coverage_b["branches"]) || {} if SimpleCov.branch_coverage?
         combination
       end
     end

spec/combine/results_combiner_spec.rb

@@ -101,6 +101,10 @@
       it "has proper results for three.rb" do
         expect(subject[source_fixture("three.rb")]["lines"]).to eq([nil, 3, 7])
       end
+
+      it "always returns a Hash object for branches" do
+        expect(subject[source_fixture("three.rb")]["branches"]).to eq({}) if SimpleCov.branch_coverage_supported?
+      end
     end
   end