client-go/rest: check if url is nil to prevent nil pointer dereference

Signed-off-by: André Martins <aanm90@gmail.com>

Kubernetes-commit: fa1d4c327716ae117120311f566d26abff9d91ad

Author: aanm

rest/request.go

@@ -519,14 +519,17 @@ func (r Request) finalURLTemplate() url.URL {
 		newParams[k] = v
 	}
 	r.params = newParams
-	url := r.URL()
+	u := r.URL()
+	if u == nil {
+		return url.URL{}
+	}
 
-	segments := strings.Split(url.Path, "/")
+	segments := strings.Split(u.Path, "/")
 	groupIndex := 0
 	index := 0
 	trimmedBasePath := ""
-	if url != nil && r.c.base != nil && strings.Contains(url.Path, r.c.base.Path) {
-		p := strings.TrimPrefix(url.Path, r.c.base.Path)
+	if r.c.base != nil && strings.Contains(u.Path, r.c.base.Path) {
+		p := strings.TrimPrefix(u.Path, r.c.base.Path)
 		if !strings.HasPrefix(p, "/") {
 			p = "/" + p
 		}
@@ -537,7 +540,7 @@ func (r Request) finalURLTemplate() url.URL {
 		groupIndex = 1
 	}
 	if len(segments) <= 2 {
-		return *url
+		return *u
 	}
 
 	const CoreGroupPrefix = "api"
@@ -555,11 +558,11 @@ func (r Request) finalURLTemplate() url.URL {
 		// outlet here in case more API groups are added in future if ever possible:
 		// https://kubernetes.io/docs/concepts/overview/kubernetes-api/#api-groups
 		// if a wrong API groups name is encountered, return the {prefix} for url.Path
-		url.Path = "/{prefix}"
-		url.RawQuery = ""
-		return *url
+		u.Path = "/{prefix}"
+		u.RawQuery = ""
+		return *u
 	}
-	//switch segLength := len(segments) - index; segLength {
+	// switch segLength := len(segments) - index; segLength {
 	switch {
 	// case len(segments) - index == 1:
 	// resource (with no name) do nothing
@@ -582,8 +585,8 @@ func (r Request) finalURLTemplate() url.URL {
 			segments[index+3] = "{name}"
 		}
 	}
-	url.Path = path.Join(trimmedBasePath, path.Join(segments...))
-	return *url
+	u.Path = path.Join(trimmedBasePath, path.Join(segments...))
+	return *u
 }
 
 func (r *Request) tryThrottleWithInfo(ctx context.Context, retryInfo string) error {