Steps to reproduce:
1. Open any Unity project
2. Add two Scenes to Build list under File>Build Settings
3. Open up ProjectSettings\EditorBuildSettings.asset under your Project folder
4. Delete the path, guid and make sure enabled is set to 1, so it looks like this:

- enabled: 1
path: Assets/Scenes/SampleScene.unity
guid: 99c9720ab356a0642a771bea13969a05
- enabled: 1
path:
guid:

5. Switch to Unity and try building the project.

Expected result: should probably result in a more elegant/behind the scenes removal of the bad Scene entry
Actual result: Unity throws the following error:

UnityEditor.BuildPlayerWindow+BuildMethodException: '' is an incorrect path for a scene file. BuildPlayer expects paths relative to the project folder.
at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (BuildPlayerOptions options) [0x00207] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:172
at UnityEditor.BuildPlayerWindow.CallBuildMethods (Boolean askForBuildLocation, BuildOptions defaultBuildOptions) [0x00050] in /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:83
UnityEngine.DebugLogHandler:Internal_Log(LogType, String, Object)
UnityEngine.DebugLogHandler:LogFormat(LogType, Object, String, Object[])
UnityEngine.Logger:Log(LogType, Object)
UnityEngine.Debug:LogError(Object)
UnityEditor.BuildPlayerWindow:CallBuildMethods(Boolean, BuildOptions) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs:88)
UnityEditor.BuildPlayerWindow:BuildPlayerAndRun(Boolean) (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindow.cs:173)
UnityEditor.BuildPlayerWindow:BuildPlayerAndRun() (at /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindow.cs:167)

(Filename: /Users/builduser/buildslave/unity/build/Editor/Mono/BuildPlayerWindowBuildMethods.cs Line: 88)

The project must be reopened for it to work again.

Reproduced with: 2017.2.1p1, 2017.4.5f1, 2018.1.4f1, 2018.3.0a1

Note: the user came to this issue by chance so all subsequent reproductions were made by manually removing relevant information from EditorBuildSettings file.