[apps/shared] Fixed a small mistake in parameter_text_field_delegate.cpp

In this commit, there was a small oversight in 7a4ee746b2, which caused https://github.com/numworks/epsilon/issues/1570

apps/shared/parameter_text_field_delegate.cpp

@@ -5,6 +5,7 @@ namespace Shared {
 
 bool ParameterTextFieldDelegate::textFieldDidReceiveEvent(TextField * textField, Ion::Events::Event event) {
   if (event == Ion::Events::Backspace && !textField->isEditing()) {
+    textField->reinitDraftTextBuffer();
     textField->setEditing(true);
     return true;
   }