updated for version 7.4.145
Problem: getregtype() does not return zero for unknown register.
Solution: Adjust documention: return empty string for unknown register.
Check the register name to be valid. (Yukihiro Nakadaira)
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index be0e667..f8f3b99 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -3460,7 +3460,7 @@
"v" for |characterwise| text
"V" for |linewise| text
"<CTRL-V>{width}" for |blockwise-visual| text
- 0 for an empty or unknown register
+ "" for an empty or unknown register
<CTRL-V> is one character with value 0x16.
If {regname} is not specified, |v:register| is used.