Fix a divide by 0 bug in `root()` (lib2.bc)

gen/lib2.bc

@@ -110,7 +110,7 @@ define root(x,n){
 	if(n<0)sqrt(n)
 	n=n$
 	if(n==0)x/n
-	if(n==1)return x
+	if(x==0||n==1)return x
 	if(n==2)return sqrt(x)
 	s=scale
 	scale=0

tests/bc/lib2.txt

@@ -84,6 +84,12 @@ cbrt(27)
 cbrt(-27)
 cbrt(4096)
 cbrt(-4096)
+root(0, 3)
+root(0, 4)
+root(0, 5)
+root(0.0000000000000, 3)
+root(0.0000000000000, 4)
+root(0.0000000000000, 5)
 root(16, 4)
 root(3125, 5)
 root(-3125, 5)

tests/bc/lib2_results.txt

@@ -84,6 +84,12 @@
 -3.00000000000000000000
 16.00000000000000000000
 -16.00000000000000000000
+0
+0
+0
+0
+0
+0
 2.00000000000000000000
 5.00000000000000000000
 -5.00000000000000000000