bad interpreter: No such file or directory

In XCode I ran into an error which was the result of a (my) bad merge that caused this problem when building an app:

/bin/sh: /Users/strefethen/github/iPhoneGeo/Build/iPhoneGeo/Build/Intermediates/iPhoneGeo.build/Debug-iphonesimulator/iPhoneGeo.build/Script-22C5773E1BB449FF00E72A71.sh: (null): bad interpreter: No such file or directory

The issue was that the Shell command for the Build Phase had gotten removed:

Screen Shot 2015-09-24 at 11.17.33 AM
This caused Xcode to insert the following line at the top of the build script and thus the above error:
#!(null)
Simply restoring the Shell setting above to “/bin/sh” corrected the issue.