Description: 
While following the guide "Using Mail Merge" https://wiki.documentfoundation.org/images/3/3c/WG4211-UsingMailMerge.pdf paragraph "Creating a form letter", a crash occours on step 6d.

Steps:
1)open calc; 
2)insert the data;
3)open writer;
4)file->wizards->Adress data source;
5)select other external data source and then click on next button;
6)click the Settings button;
7)select Spreadsheet on the database type;
8)click Browse and navigate to the spreadsheet that contains the address 
9)information;
10)click on next button;
11)click finish;
12)View > Data sources;
13)find the data source that you wish to use for the form letter;
14)click in the field heading and drag it to the appropriate point in the letter;
15)Insert > Fields > Other;
16)select the Functions tab and then click on Hidden Paragraph in the Type column;
17)now click in the Condition box and enter the details of the condition that defines a blank address field. It has the general form of:![Database.Table.Database field];
18)and then click on insert button and close the dialog;
19)now save the document on the desktop;
20)close the document using the X button on the window and now writer will crash.

Affected versions:
Versione: 5.1.3.2
Build ID: 10m0(Build:2)
Thread CPU: 2; Versione SO: Linux 4.1; Resa interfaccia: predefinito; 
Versione locale: it-IT (it_IT.UTF-8)
OS: openSUSE Leap 42.1 (x86_64)

Versione: 5.1.3.2
Build ID: 644e4637d1d8544fd9f56425bd6cec110e49301b
Thread CPU: 2; Versione SO: Linux 4.1; Resa interfaccia: predefinito; 
Versione locale: it-IT (it_IT.UTF-8)
OS: openSUSE Leap 42.1 (x86_64)

Not affected 
Versione: 5.0.6.3
Build ID: 490fc03b25318460cfc54456516ea2519c11d1aa
Versione locale: it-IT (it_IT.UTF-8)
OS: openSUSE Leap 42.1 (x86_64)

Versione: 4.4.7.2
Build ID: f3153a8b245191196a4b6b9abd1d0da16eead600
Versione locale: it_IT.UTF-8
OS: openSUSE Leap 42.1 (x86_64)

Versione: 4.3.7.2
Build ID: 8a35821d8636a03b8bf4e15b48f59794652c68ba
OS: openSUSE Leap 42.1 (x86_64)

Expected behavior: 
The hidden paragraph is inserted and the user can closes the dialog, saves and close the document.

Current behavior:
The hidden paragraph is inserted, the user can closes the dialog and saves the document.When the user closes the document using the X button on the window LibreOffice crashes.