Remove nil check (#493)

As the length of a nil slice is defined as 0, the nil check is
redundand. (suggested by golanci-lint/gosimple)

check/test.go

@@ -244,8 +244,8 @@ func executeJSONPath(path string, jsonInterface interface{}) (string, error) {
 }
 
 func allElementsValid(s, t []string) bool {
-	sourceEmpty := s == nil || len(s) == 0
-	targetEmpty := t == nil || len(t) == 0
+	sourceEmpty := len(s) == 0
+	targetEmpty := len(t) == 0
 
 	if sourceEmpty && targetEmpty {
 		return true