Describe the problem
When opening measure-based view of a source with parts, getParts.xql throws an error:

/db/apps/Edirom-Online/data/xql/getParts.xqlexerr:ERROR The actual return type does not match the sequence type declared in the function's signature: eutil:getLanguageString(xs:string, xs:string*, xs:string) xs:string. Expected cardinality: exactly one, got 0. [at line 264, column 41, source: /db/apps/Edirom-Online/data/xqm/eutil.xqm]

In function:
eutil:getLanguageString(xs:string, xs:string*, xs:string) [227:12:/db/apps/Edirom-Online/data/xqm/eutil.xqm]
eutil:getPartLabel(node(), xs:string) [32:22:/db/apps/Edirom-Online/data/xqm/eutil.xqm]

i was able to track the problem down:
getParts.xql will try to translate the names of the parts with the edirom-lang-(de|en).xml-file
(e.g. <entry key="perfMedium.perfRes.voice" value="Voice (singing)"/>)
by calling eutil:getPartLabel(), which calls eutil:getLanguageString() to resolve the lang-key from the lang-file.
if the key (in my case perfMedium.perfRes.Set (3) Violoncello/Contrabbasso) does not exist, the return-value will be empty and not match the functions return key and an error is thrown.

explicitly checking the the returned value from the lang-file and returning an empty string if nothing was returned, solved the error: adding
let $string := if(string-length($string) != 0) then ($string) else ("")
to the end of eutil:getLanguageString()

i cant tell if there might be any sideeffects by adding this line. can someone confirm that its safe?

it probably might be good to rethink translations (esp. of part-names) and implement them consequently (goto-menu with parts doesnt make use of translations so far).
Rel #155

To Reproduce

1. Setup Exist with current Edirom-Online develop and open-faust data
2. Open source A3, go to measure-based view
3. Nothing will be shown, because getParts.xql throws error

Expected behavior
no error should be thrown and the name of the parts should be displayed

Data
open-faust dataset: https://git.uni-paderborn.de/kio/open-faust

Edirom information

• Edirom-Online version: v1.0.0-beta.7 on develop-branch (ae50cb9)

Environment information

• Chrome
• MEI-Version of file: 3.0.0