patch 8.2.2905: no error when defaults.vim cannot be loaded

Problem:    No error when defaults.vim cannot be loaded.
Solution:   Add an error message. (Christian Brabandt, closes #8248)
diff --git a/runtime/doc/starting.txt b/runtime/doc/starting.txt
index 469ec0c..d4e8cf8 100644
--- a/runtime/doc/starting.txt
+++ b/runtime/doc/starting.txt
@@ -1036,7 +1036,7 @@
 
 
 Defaults without a .vimrc file ~
-							*defaults.vim*
+							*defaults.vim* *E1187*
 If Vim is started normally and no user vimrc file is found, the
 $VIMRUNTIME/defaults.vim script is loaded.  This will set 'compatible' off,
 switch on syntax highlighting and a few more things.  See the script for