Comparing AST's that are unequal size args can panic

[araddon]

Panic on Equal()

panic(0x7ff8d34a8ba0, 0xc4200100c0) 
	/usr/local/go/src/runtime/panic.go:458 +0x243 
github.com/lytics/lio/vendor/github.com/araddon/qlbridge/expr.(*ArrayNode).Equal(0xc48bbfc390, 0x7ff8d454e780, 0xc48bbfc4b0, 0x1) 
	/home/go/src/github.com/lytics/lio/vendor/github.com/araddon/qlbridge/expr/node.go:1979 +0x11a 
github.com/lytics/lio/vendor/github.com/araddon/qlbridge/expr.(*BinaryNode).Equal(0xc4a2f15da0, 0x7ff8d454e800, 0xc4a2f15740, 0x1) 
	/home/go/src/github.com/lytics/lio/vendor/github.com/araddon/qlbridge/expr/node.go:1387 +0x193 
github.com/lytics/lio/vendor/github.com/araddon/qlbridge/expr.(*BooleanNode).Equal(0xc4a2f15620, 0x7ff8d454e880, 0xc4a2f15c80, 0x1c) 
	/home/go/src/github.com/lytics/lio/vendor/github.com/araddon/qlbridge/expr/node.go:1529 +0x190 
github.com/lytics/lio/vendor/github.com/araddon/qlbridge/rel.(*FilterStatement).Equal(0xc49e9eb290, 0xc49e9ebc30, 0x0) 
	/home/go/src/github.com/lytics/lio/vendor/github.com/araddon/qlbridge/rel/filter.go:147 +0x225