Bug 39596: Adding a label when the second indicator of MARC 780/785 is void

Test plan:

1. Go to Administration > MARC Bibliographic framework
2. On the right side of the default framework, click on "Actions" >
   "MARC Structure"
3. Search for field 780
4. Click on "Actions" > "Edit subfields"
5. Click on the "t" tab
6. Check "Editor" under the "Visibility" section
7. Click on "Save Changes"
8. Repeat steps 1 to 7 for field 785$t
9. Have or create a record with a value for 780 and 785 with the first
   indicator at 0 and the other left empty
10. Go see the record on the OPAC
11. Notice that in Normal View, the value entered for 780 and 785 do not
    have labels
12. Apply the patch
13. There are now labels

Signed-off-by: Owen Leonard <oleonard@myacpl.org>

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit a3bfa55919)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>

koha-tmpl/opac-tmpl/bootstrap/en/xslt/MARC21slim2OPACDetail.xsl

@@ -1579,6 +1579,9 @@
                             <xsl:when test="@ind2=7">
                                 <span class="label">Separated from:</span>
                             </xsl:when>
+                            <xsl:otherwise>
+                                <span class="label">Preceding entry:</span>
+                            </xsl:otherwise>
                         </xsl:choose>
                         <xsl:text> </xsl:text>
 
@@ -1667,6 +1670,9 @@
                             <xsl:when test="@ind2=8">
                                 <span class="label">Changed back to:</span>
                             </xsl:when>
+                            <xsl:otherwise>
+                               <span class="label">Succeeding entry:</span>
+                            </xsl:otherwise>
                         </xsl:choose>
                         <xsl:text> </xsl:text>