fix: unbind error (#1094)

packages/core/database/src/fields/has-one-field.ts

@@ -154,19 +154,27 @@ export class HasOneField extends RelationField {
     database.removePendingField(this);
     // 如果关系表内没有显式的创建外键字段，删除关系时，外键也删除掉
     const tcoll = database.collections.get(this.target);
+
+    if (tcoll) {
       const foreignKey = this.options.foreignKey;
+
       const field = tcoll.findField((field) => {
         if (field.name === foreignKey) {
           return true;
         }
         return field.type === 'belongsTo' && field.foreignKey === foreignKey;
       });
+
       if (!field) {
         tcoll.model.removeAttribute(foreignKey);
       }
+    }
 
     const association = collection.model.associations[this.name];
+
+    if (association) {
       this.database.referenceMap.removeReference(this.reference(association));
+    }
 
     this.clearAccessors();
     // 删掉 model 的关联字段