fixed arg validation

tools/rest/excerpt_modifier.go

@@ -47,7 +47,7 @@ func newExcerptModifier(args ...string) (*excerptModifier, error) {
 	}
 
 	max := cast.ToInt(args[0])
-	if max == 0 {
+	if max <= 0 {
 		return nil, errors.New("max argument must be > 0")
 	}
 

tools/rest/excerpt_modifier_test.go

@@ -28,6 +28,16 @@ func TestNewExcerptModifier(t *testing.T) {
 			[]string{"something"}, // should fallback to 0 which is not allowed
 			true,
 		},
+		{
+			"negative numeric max argument",
+			[]string{"-1"},
+			true,
+		},
+		{
+			"zero numeric max argument",
+			[]string{"0"},
+			true,
+		},
 		{
 			"numeric max argument",
 			[]string{"12"},