Avoid trying to edit a non-existing file (#477)

The previous implementation was inconsistent, sometimes it would
inherit the name of the parent folder of the current directory.

Other scenarios i encountered were:
1. Yield a empty search result, and try to edit. It would seemingly
   randomly select a file or folder
2. What would happen in a root path without any files residing?

src/nnn.c

@@ -5453,6 +5453,8 @@ nochange:
 
 			if (ndents)
 				mkpath(path, dents[cur].name, newpath);
+			else if (sel == SEL_EDIT) /* Avoid trying to edit a non-existing file */
+				goto nochange;
 
 			switch (sel) {
 			case SEL_REDRAW: