NFC: Improve length(EXPR) code

Author: pfitzseb

src/spec.jl

@@ -280,8 +280,8 @@ end
 function Base.length(x::EXPR)
     headof(x) === :NONSTDIDENTIFIER && return 0
     headof(x) === :flatten && return length(Iterating._flatten_lhs(x))
-    n = x.args isa Nothing ? 0 : length(x.args)
-    n += x.trivia !== nothing ? length(x.trivia) : 0
+    n = x.args === nothing ? 0 : length(x.args)
+    n += x.trivia === nothing ? 0 : length(x.trivia)
     x.head isa EXPR && !(x.head.span === 0) && (n += 1)
     return n
 end