renderFormElements for richtext no longer showing existing content for some external modules

[jasonabird]

Some modules (specifically mxCalendar) that uses renderFormElements no longer shows existing content in richtext fields.

[Jako]

There is a bug in your code: $field_value should be only $default_text if $field_value is empty.

The original code was changed from something like this:
$field_value = ($field_value != '') ? $field_value : $default_text;

[jasonabird]

Great catch. Updated with that fix and validated also fixes for external modules such as mxcalendar that was using renderFormElements.

[MrSwed]

@@eval stopped working
need check again

reverts: #1016