Don't JSON.parse(nil)

app/models/dialog_field_drop_down_list.rb

@@ -90,6 +90,7 @@ def default_value_included?(values_list)
   end
 
   def coerce_default_value_into_proper_format
+    return unless default_value
     unless JSON.parse(default_value).kind_of?(Array)
       self.default_value = Array.wrap(default_value).to_json
     end

spec/models/dialog_field_drop_down_list_spec.rb

@@ -146,9 +146,25 @@
         allow(DynamicDialogFieldValueProcessor).to receive(:values_from_automate).with(dialog_field).and_return(values)
       end
 
-      it "uses the given value as the default" do
-        dialog_field.initialize_with_given_value("test")
-        expect(dialog_field.default_value).to eq(["test"].to_json)
+      context "given value is a string" do
+        it "uses the given value as the default" do
+          dialog_field.initialize_with_given_value("test")
+          expect(dialog_field.default_value).to eq(["test"].to_json)
+        end
+      end
+
+      context "given value is an array" do
+        it "uses the given value as the default" do
+          dialog_field.initialize_with_given_value(["test"])
+          expect(dialog_field.default_value).to eq(["test"].to_json)
+        end
+      end
+
+      context "given value is nil" do
+        it "uses the given value as the default" do
+          dialog_field.initialize_with_given_value(nil)
+          expect(dialog_field.default_value).to eq(nil)
+        end
       end
     end
   end