fix: prevent panic in PostForm getters when Request is nil

Signed-off-by: Sai Asish Y <say.apm35@gmail.com>

context.go

@@ -649,6 +649,9 @@ func (c *Context) initFormCache() {
 	if c.formCache == nil {
 		c.formCache = make(url.Values)
 		req := c.Request
+		if req == nil {
+			return
+		}
 		if err := req.ParseMultipartForm(c.engine.MaxMultipartMemory); err != nil {
 			if !errors.Is(err, http.ErrNotMultipart) {
 				debugPrint("error on parse multipart form array: %v", err)

context_test.go

@@ -3955,3 +3955,13 @@ func BenchmarkGetMapFromFormData(b *testing.B) {
 		})
 	}
 }
+
+func TestContextPostFormNoRequest(t *testing.T) {
+	c, _ := CreateTestContext(httptest.NewRecorder())
+
+	value, ok := c.GetPostForm("key")
+	assert.False(t, ok)
+	assert.Empty(t, value)
+	assert.Empty(t, c.PostForm("key"))
+	assert.Equal(t, "fallback", c.DefaultPostForm("key", "fallback"))
+}