From the 0.9.2.0 release:
gtkdatabox_ruler.c:1439:47: warning:
suggest parentheses around comparison in operand of '&' [-Wparentheses]
gtkdatabox_ruler.c:1442:47: warning:
suggest parentheses around comparison in operand of '&' [-Wparentheses]
gtkdatabox_ruler.c:1444:47: warning:
suggest parentheses around comparison in operand of '&' [-Wparentheses]
It looks like someone has got '&' and '&&' mixed up.
fixed in 5fe522a6 and released in 0.9.3.0