Flutter white screen on app after adding widget

Question

I have run into an issue that has my head itching a bit. When adding a new element to my page (using ReactiveDateTimePicker) and running the code I am met with a page that displays nothing but white (The appbar and hamburger menu at the top still show though).

Without the added code the page looks like the screenshot below.

However once I add in the code, the screen looks like the screenshot below

The code for the page is quite lengthy, so I am adding it on codepen for easier visibility. Here is the link to the full code. The section I added which caused the error is below

ReactiveForm(
                      formGroup: _form,
                      child: ListView(children: <Widget>[
                        Padding(
                          padding: EdgeInsets.only(top: 0, left: 0, right: 0),
                          child: ReactiveDateTimePicker(
                            formControlName: 'child_details.dateOfBirth',
                            type: ReactiveDatePickerFieldType.date,
                            firstDate: DateTime(DateTime.now().year - 18, 1, 1),
                            lastDate: DateTime.now()
                                .subtract(Duration(days: 2 * 365)),
                            datePickerEntryMode: DatePickerEntryMode.calendar,
                            showClearIcon: false,
                            validationMessages: {
                              '_requiredYounger120': (error) =>
                                  'Really? More than 120 years old?'
                            },
                            decoration: InputDecoration(
                              labelText: 'Date of birth',
                              border: UnderlineInputBorder(),
                              helperText: '',
                            ),
                            //locale: Localizations.localeOf(context),
                            builder: (BuildContext context, Widget child) {
                              return Theme(
                                data: ThemeData.light().copyWith(
                                  primaryColor: Theme.of(context).primaryColor,
                                  accentColor: Theme.of(context).accentColor,
                                  colorScheme: ColorScheme.light(
                                      primary: Theme.of(context).primaryColor),
                                  buttonTheme: ButtonThemeData(
                                      textTheme: ButtonTextTheme.primary),
                                ),
                                child: child,
                              );
                            },
                          ),
                        ),
                      ])),

I am getting the error after I add the code from line 1297 - 1335. This happens on both Android and iOS