'FOAM FATAL IO ERROR' in tut externalSolarLoad

Summary

In externalSolarLoad, when i turn on the DebugSwitches (faceShading and solarCalculator), a solver returns "FOAM FATAL IO ERROR" in the process of calculation.

Steps to reproduce

As mentioned the above Summary, see a logfile.

logOnDebugSwitches

Example case

tutorial case 'externalSolarLoad'

What is the current bug behaviour?

(What actually happens)

What is the expected correct behavior?

(What you should see instead)

Relevant logs and/or images

--> FOAM FATAL IO ERROR: 
Bad token - could not get word

file: input at line 0.

    From function Foam::Istream& Foam::operator>>(Foam::Istream&, Foam::word&)
    in file primitives/strings/word/wordIO.C at line 45.

FOAM exiting

Environment information

(OpenFOAM version : v1812) (Operating system : ubuntu18.04) (Hardware info : intel x86_64)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)