qv4l2: fix coverity defect

qv4l2: fix coverity defect

** CID 1225222:  Array compared against 0  (NO_EFFECT)
/utils/qv4l2/ctrl-tab.cpp: 150 in ApplicationWindow::addTabs(int *)()

*** CID 1225222:  Array compared against 0  (NO_EFFECT)
/utils/qv4l2/ctrl-tab.cpp: 150 in ApplicationWindow::addTabs(int *)()
144     		QVBoxLayout *vbox = new QVBoxLayout(t);
145     		QWidget *w = new QWidget(t);
146
147     		vbox->addWidget(w);
148
149     		QGridLayout *grid = new QGridLayout(w);
>>>     CID 1225222:  Array compared against 0  (NO_EFFECT)
>>>     Comparing an array to null is not useful: "(char *)qctrl.name".
150     		if((char *)qctrl.name) {
151     			QLabel *title_tab = new QLabel((char *)qctrl.name, parentWidget());
152     			QFont f = title_tab->font();
153     			f.setBold(true);
154     			title_tab->setFont(f);
155     			grid->addWidget(title_tab, m_row, m_col, 1, m_cols, Qt::AlignLeft);

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>