Getting following error: Unknown member PDM_MAIN_F

Line causing error:
pdm_var.pdm_main_f.Label1.Caption = AllT(pdm_global_vars.appStatusMessage)

The following line of code just before error line generates an 'O':
? Type('pdm_var.pdm_main_f')

How can I trap around this error and do other code? What might be the reason this is happening in the first place?