Add a catch when running handler

Add a spec

lib/grape/middleware/error.rb

@@ -116,16 +116,19 @@ def run_rescue_handler(handler, error, endpoint)
           handler = public_method(handler)
         end
 
+        handler_exception = nil
         response = catch(:error) do
           handler.arity.zero? ? endpoint.instance_exec(&handler) : endpoint.instance_exec(error, &handler)
+        rescue StandardError => e
+          handler_exception = e
         end
 
         if error?(response)
           error_response(response)
         elsif response.is_a?(Rack::Response)
           response
         else
-          run_rescue_handler(method(:default_rescue_handler), Grape::Exceptions::InvalidResponse.new, endpoint)
+          run_rescue_handler(method(:default_rescue_handler), handler_exception || Grape::Exceptions::InvalidResponse.new, endpoint)
         end
       end
 

spec/grape/api_spec.rb

@@ -4693,4 +4693,23 @@ def uniqe_id_route
 
     it { is_expected.to be_bad_request }
   end
+
+  context "when rescue_from's block raises an error" do
+    subject { last_response.body }
+
+    let(:api) do
+      Class.new(described_class) do
+        rescue_from :all do
+          raise ArgumentError, 'This one!'
+        end
+        get { raise ArgumentError, 'Oops!' }
+      end
+    end
+
+    let(:app) { api }
+
+    before { get '/' }
+
+    it { is_expected.to eq('This one!') }
+  end
 end