avoid panic when storing a nil pointer in cached_mysql (#8020)

related to #7420, this improves the logic of the clone function in cached_mysql to properly handle nil and nil pointers.

changes/issue-7420-config-panics

@@ -0,0 +1 @@
+* Fixed a server panic happening when a team was edited via yaml without an `agent_options` key.

server/datastore/cached_mysql/cached_mysql.go

@@ -35,6 +35,10 @@ func clone(v interface{}) (interface{}, error) {
 		return cloner.Clone()
 	}
 
+	if v == nil {
+		return nil, nil
+	}
+
 	// Use reflection to initialize a clone of v of the same type.
 	vv := reflect.ValueOf(v)
 
@@ -43,6 +47,9 @@ func clone(v interface{}) (interface{}, error) {
 	isPtr := false
 	if vv.Kind() == reflect.Ptr {
 		isPtr = true
+		if vv.IsNil() {
+			return nil, nil
+		}
 		vv = vv.Elem()
 	}
 

server/datastore/cached_mysql/cached_mysql_test.go

@@ -15,6 +15,8 @@ import (
 )
 
 func TestClone(t *testing.T) {
+	var nilRawMessage *json.RawMessage
+
 	tests := []struct {
 		name string
 		src  interface{}
@@ -61,6 +63,16 @@ func TestClone(t *testing.T) {
 			src:  &[]string{"foo", "bar"},
 			want: &[]string{"foo", "bar"},
 		},
+		{
+			name: "nil",
+			src:  nil,
+			want: nil,
+		},
+		{
+			name: "nil pointer",
+			src:  nilRawMessage,
+			want: nil,
+		},
 	}
 
 	for _, tc := range tests {