QGIS » QGIS Application

In Map Composer I try make 11 sides long report width attribute table, where I has modified one attribute through function editor (python, ogr, execute sql). When I pass shortcut of tree the function returns latin and czech name of tree. Everything works quite fine but attribute table has some rows where attribute "name of tree" is empty. Maybe 10 - 15 rows in 250 rows long attribute table. When I update table, empty places are shifted, but count of white places will not change.

There is code of python function:

from qgis.core import *
from qgis.gui import *
import os

@qgsfunction(args='auto', group='Custom')
def nacistTabDrUp(value1, feature, parent):

    def nacistTabDr():
        from osgeo import ogr
        prjpath = QgsProject.instance().fileName()
        con = ogr.Open(os.path.dirname(prjpath) + "/tab_dr.dbf")  
        print(con)
        rows = con.ExecuteSQL("SELECT * FROM tab_dr")
        tax_lat_ = {}
        tax_cz_ = {}

        for i in rows:
            tax_lat_[i.GetField("znacka")] = i.GetField("TAXON")
            if i.GetField("znacka") == "PAREZ":
                tax_cz_[i.GetField("znacka")] = "" 
            else:
                tax_cz_[i.GetField("znacka")] = i.GetField("cs_nazev")
        return (tax_lat_, tax_cz_) 
        con.close()

    def doplnitNazev(zkrt):
        tax_latx = {}
        tax_czx = {}
        tax_latx, tax_czx = nacistTabDr()
        try: return (tax_latx[zkrt] +"\
"+ tax_czx[zkrt])
        except KeyError: return[zkrt]

    return unicode(doplnitNazev(value1))