fixed display of ErrorMessage for source code

[5P5]

how it looks:

Syntax error in text: can not read a block mapping entry; a multiline key may not be an implicit key (3:2) 1 | a: 2 | b 3 | c: ------^

how it should look:

Syntax error in text: can not read a block mapping entry; a multiline key may not be an implicit key (3:2)

 1 | a:
 2 | b
 3 | c:
------^