Reproduction steps:
1. Create a new Unity project.
2. Go to player settings and switch platform to iOS.
3. Choose Run in Xcode as Debug.
4. Click Build and Run.
5. Choose a name and click Save.
6. As soon as you are able to, click Build and Run again.
7. Save as the same name and click Replace.
- Editor crashes after some time:

#0 0x00000100415461 in PPtr<Object>::operator Object*() const
#1 0x00000102348728 in BuildReporting::PrintLegacyBuildReport(BuildReporting::BuildReport const&)
#2 0x0000010106046d in BuildPlayer(BuildPlayerSetup const&, BuildReporting::BuildReport&)
#3 0x0000010243c434 in BuildPipeline_CUSTOM_BuildPlayerInternalNoCheck(MonoArray*, MonoString*, MonoString*, BuildTargetPlatformGroup, BuildTargetPlatform, BuildPlayerOptions, unsigned char)
#4 0x0000011f9229c2 in (wrapper managed-to-native) UnityEditor.BuildPipeline:BuildPlayerInternalNoCheck (string[],string,string,UnityEditor.BuildTargetGroup,UnityEditor.BuildTarget,UnityEditor.BuildOptions,bool) + 0xd2 (0x11f9228f0 0x11f9229f1) [0x13740c660 - Unity Child Domain]
#5 0x0000011f92226a in UnityEditor.BuildPlayerWindow/DefaultBuildMethods:BuildPlayer (UnityEditor.BuildPlayerOptions) + 0xc5a (0x11f921610 0x11f92262a) [0x13740c660 - Unity Child Domain]
...

Reproduced with:
5.5.4f1, 2017.1.0b9, 2017.2.0a4