fix(context): prevent nil pointer dereference in initFormCache when Request is nil (fix #4772)

context.go

@@ -648,13 +648,18 @@ func (c *Context) PostFormArray(key string) (values []string) {
 func (c *Context) initFormCache() {
 	if c.formCache == nil {
 		c.formCache = make(url.Values)
-		req := c.Request
+		if c.Request != nil {
-		if err := req.ParseMultipartForm(c.engine.MaxMultipartMemory); err != nil {
+			var maxMemory int64 = defaultMultipartMemory
-			if !errors.Is(err, http.ErrNotMultipart) {
+			if c.engine != nil {
-				debugPrint("error on parse multipart form array: %v", err)
+				maxMemory = c.engine.MaxMultipartMemory
 			}
+			if err := c.Request.ParseMultipartForm(maxMemory); err != nil {
+				if !errors.Is(err, http.ErrNotMultipart) {
+					debugPrint("error on parse multipart form array: %v", err)
+				}
+			}
+			c.formCache = c.Request.PostForm
 		}
-		c.formCache = req.PostForm
 	}
 }
 

context_test.go

@@ -3955,3 +3955,24 @@ func BenchmarkGetMapFromFormData(b *testing.B) {
 		})
 	}
 }
+
+func TestContextPostFormWithoutRequest(t *testing.T) {
+	c, _ := CreateTestContext(httptest.NewRecorder())
+	c.Request = nil
+
+	val, ok := c.GetPostForm("key")
+	assert.False(t, ok)
+	assert.Empty(t, val)
+
+	val = c.PostForm("key")
+	assert.Empty(t, val)
+
+	val = c.DefaultPostForm("key", "default_val")
+	assert.Equal(t, "default_val", val)
+
+	vals := c.PostFormArray("key")
+	assert.Empty(t, vals)
+
+	mapVals := c.PostFormMap("key")
+	assert.Empty(t, mapVals)
+}