tdf#100726 improved readability of OUString/Ostring concatenation

changed variable aResult to use concationation operator + instead of +=

Change-Id: I1547a869a9b6ede6e64727a1048232caf404acb7
Reviewed-on: https://gerrit.libreoffice.org/43340Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Muhammet Kara <muhammet.kara@pardus.org.tr>

svl/source/passwordcontainer/passwordcontainer.cxx

@@ -67,8 +67,8 @@ static OUString createIndex(const vector< OUString >& lines)
             }
             else
             {
-                aResult += "_";
-                aResult += OUString::number(  *pLine, 16 );
+                aResult += "_"
+                        + OUString::number(  *pLine, 16 );
             }
 
             pLine++;