Description:
Libre Office Writer/Base - MailMerge "Label Document" Error.
Error Message: "The data source "BizMailingListData" was not found."

- Label documents only work for MailMerge printing during the LibreOffice Writer session in which they are created. During any other LibreOffice Writer session they produce an error message. (See attached sample error message.)

- This requires that a new label document is created each time labels are printed.  Saved label documents that are used in a later LibreOffice Writer session are useless and always produce an error. 

- This bug is with the MailMerge feature which involves both LibreOffice Writer and LibreOffice Base.  However, the bug appears to be in the source code for LibreOffice Writer.

Steps to Reproduce:
REPRODUCING THE BUG:
1. To produce the error create a MailingList table in LibreOffice Base similar to the one attached. (See Sample Database file)  
2. In LibreOffice Base, create a label document from the LibreOffice Base table. 
(File > New > Label) 
(See Sample label document)
3. In the LibreOffice Base label creation window, add the appropriate fields from the right (i.e. database fields) to the leftside (i.e. label). 
4. Click on the "New Document" button to create the new LibreOffice Writer label document. 
4. Now print the LibreOffice Writer Label document. 
(File > Print...) 
-The MailMerge dialog appears: 
"Your document contains address database fields. Do you want to print a form letter?" 
-Click on the "Yes" button.
-The labels should print normally.
5. Save and close the LibreOffice Writer Label Document.   
6. Re-open the Label Document file and attempt to print it as above. (File > Print...)
-The MailMerge dialog appears 
"Your document contains address database fields. Do you want to print a form letter?" 
-Click on the "Yes" button.
-This time the error message appears and the label document fails to print. 

Actual Results:
Error Message: "The data source "BizMailingListData" was not found."

Expected Results:
Successful printing of address labels from existing Base Database. 


Reproducible: Always


User Profile Reset: No



Additional Info:
NOTE: 
- I discovered this bug while following the instructions in the LibreOffice Help documentation: 
- (See Search Term: labels;creating and synchronizing)
- (See Search Term: labels;from databases)

LIBREOFFICE VERSION - In which bug was discovered:
Version: 6.1.4.2
Build ID: libreoffice-6.1.4.2-snap1
CPU threads: 4; OS: Linux 4.15; UI render: default; VCL: gtk3; 
Locale: en-US (en_US.UTF-8); Calc: group threaded
(The release was provided by Canonical.)

OPERATING SYSTEM - On which LibreOffice was installed. 
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 18.04.1 LTS
Release:	18.04
Codename:	bionic