fmbtwindows: fixed ViewItem.bbox() to return always a tuple
fmbtwindows: fixed ViewItem.bbox() to return always a tuple

01org/fMBT,mixu-/fMBT,violep01/fMBT,yoonkiss/fMBT,01org/fMBT,mixu-/fMBT,mixu-/fMBT,violep01/fMBT,yoonkiss/fMBT,01org/fMBT,01org/fMBT,mixu-/fMBT,violep01/fMBT,yoonkiss/fMBT,mixu-/fMBT,violep01/fMBT,yoonkiss/fMBT,yoonkiss/fMBT,01org/fMBT,violep01/fMBT