fix: invalid label/flag parsing.

pkg/config/parser/labels_decode.go

@@ -21,6 +21,10 @@ func DecodeToNode(labels map[string]string, rootName string, filters ...string)
 
 		var parts []string
 		for _, v := range split {
+			if v == "" {
+				return nil, fmt.Errorf("invalid element: %s", key)
+			}
+
 			if v[0] == '[' {
 				return nil, fmt.Errorf("invalid leading character '[' in field name (bracket is a slice delimiter): %s", v)
 			}

pkg/config/parser/labels_decode_test.go

@@ -26,6 +26,15 @@ func TestDecodeToNode(t *testing.T) {
 			in:       map[string]string{},
 			expected: expected{node: nil},
 		},
+		{
+			desc: "invalid label, ending by a dot",
+			in: map[string]string{
+				"traefik.http.": "bar",
+			},
+			expected: expected{
+				error: true,
+			},
+		},
 		{
 			desc: "level 1",
 			in: map[string]string{