Steps to reproduce:

1. Open attached project
2. Open scene "testScene"
3. In hierarchy, select ScriptHolder GO and notice that Cube is passed as type of GameObject (indicated by the icon)
4. Run scene and notice that position is printed correctly
5. Open LogPositionOfTransform.cs script
6. In line 6, change type of targetObject from GameObject to Transform
7. In hierarchy, select ScriptHolder GO and notice that Cube is still passed as GameObject (indicated by icon)
8. Run scene
9. Notice that instead of printing coordinates MissingReferenceException is thrown
Expected result: Field of LogPositionOfTransform in inspector changes to "Type mismatch"

Note: After doing steps 1-6, re-assign Cube to ScriptHolder and notice that it is passed as Transform. Then in LogPositionOfTransform change type of targetObject back to GameObject. In inspector, inspect ScriptHolder GO and notice that field IS updated to "Type mismatch"

Reproduced with: 5.1.4f1, 5.4.2f1, 5.3.2p4, 5.4.0b7