Forbid the use of empty strings as tags

Some tags were wrong when the user added two commas, so this patch forbids
the use of a comma when we don't have any tags.

Signed-off-by: Tomaz Canabrava <tomaz.canabrava@intel.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/groupedlineedit.cpp

@@ -87,6 +87,8 @@ void GroupedLineEdit::addBlock(int start, int end)
 	block.start = start;
 	block.end = end;
 	block.text = text().mid(start, end - start + 1).remove(',').trimmed();
+	if (block.text.isEmpty())
+		return;
 	d->blocks.append(block);
 	viewport()->update();
 }