console: allow NULL lines in buffer

If we see a NULL line inside the buffer we assume the line is empty.
That is, we now longer abort the drawing but continue with the next
line.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

src/console_cell.c

@@ -515,7 +515,7 @@ void kmscon_buffer_draw(struct kmscon_buffer *buf, struct kmscon_font *font)
 		}
 
 		if (!line)
-			break;
+			continue;
 
 		if (line->size < buf->size_x)
 			num = line->size;