Occurs in Fiber with multiple instances of the React package (which can't share current owner).
invariant(
        inst,
        'Missing owner for string ref %s. This error is likely caused by a ' +
          'bug in React. Please file an issue.',
        mixedRef,
      );
      const stringRef = '' + mixedRef;
      
      if (
        current !== null &&
        current.ref !== null &&
        current.ref._stringRef === stringRef
      ) {
        return current.ref;
      }
      const ref = function(value) {
        const refs = inst.refs === emptyObject ? (inst.refs = {}) : inst.refs;
        if (value === null) {
          delete refs[stringRef];
        } else {
          refs[stringRef] = value;
        }
      };
      ref._stringRef = stringRef;
      return ref;
    }
  }
  return mixedRef;
}
function throwOnInvalidObjectType(returnFiber: Fiber, newChild: Object) {