Does anyone know why the matrix dl is returning an empty matrix in this code?

Hello, I am building a GUI to take import the geometry from the PDE toolbox. A button opens the PDE toolbox and makes the geometry parts global so they can be used later:

function pbn_cre_geom_Callback(hObject, eventdata, handles)
global gd ns fs dl bt
gd; ns; fs; dl; bt;
pdetool

Using the Draw menu in the PDE toolbox, the geometry is exported "Export Geometry Description, Set Formula, Labels" normally without changing any values. The values appear in the Workspace on the right. Another button needs the decomposed geometry, the required variables have been globalised again:

function pbn_sta_opt_Callback(hObject, eventdata, handles)
global gd ns sf bt dl
gd
[dl,bt]=decsg(gd,sf,ns)
dl

When the second button is pressed, gd, dl and bt are empty matrices in the command window. Does anyone have any idea why this is? THanks for your time