Fix the rule G108/pporf to handle the case when the pporf import has not name

This is causing a crash.
Signed-off-by: Cosmin Cojocar <cosmin.cojocar@gmx.ch>

rules/pprof.go

@@ -20,7 +20,7 @@ func (p *pprofCheck) ID() string {
 // Match checks for pprof imports
 func (p *pprofCheck) Match(n ast.Node, c *gosec.Context) (*gosec.Issue, error) {
 	if node, ok := n.(*ast.ImportSpec); ok {
-		if p.importPath == unquote(node.Path.Value) && p.importName == node.Name.Name {
+		if p.importPath == unquote(node.Path.Value) && node.Name != nil && p.importName == node.Name.Name {
 			return gosec.NewIssue(c, node, p.ID(), p.What, p.Severity, p.Confidence), nil
 		}
 	}

testutils/source.go

@@ -420,7 +420,22 @@ func main() {
 		fmt.Fprintf(w, "Hello World!")
 	})
 	log.Fatal(http.ListenAndServe(":8080", nil))
-}`}, 1, gosec.NewConfig()}}
+}`}, 1, gosec.NewConfig()}, {[]string{`
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"net/http/pprof"
+)
+
+func main() {
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintf(w, "Hello World!")
+	})
+	log.Fatal(http.ListenAndServe(":8080", nil))
+}`}, 0, gosec.NewConfig()}}
 	// SampleCodeG201 - SQL injection via format string
 	SampleCodeG201 = []CodeSample{
 		{[]string{`