Sensible error messages when a silly addition is performed.

Fix a test to no longer perform an invalid addition.

c/testdata

@@ -207,7 +207,7 @@ def id(x):x; 2000 as $x | def f(x):1 as $x | id([$x, x, x]); def g(x): 100 as $x
 # test backtracking through function calls and returns
 # this test is *evil*
 [[20,10][1,0] as $x | def f: (100,200) as $y | def g: [$x + $y, .]; . + $x | g; f[0] | [f][0][1] | f]
-"woo, testing!"
+999999999
 [[110.0, 130.0], [210.0, 130.0], [110.0, 230.0], [210.0, 230.0], [120.0, 160.0], [220.0, 160.0], [120.0, 260.0], [220.0, 260.0]]
 
 #