patch 8.0.1416: crash when searching for a sentence

Problem:    Crash when searching for a sentence.
Solution:   Return NUL when getting character at MAXCOL. (closes #2468)
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index 84a72e1..539e39f 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -4521,13 +4521,14 @@
 		    if (lnum != MAXLNUM)
 			curwin->w_cursor.lnum = lnum;
 		    /*
-		     * Start a forward search at the end of the line.
+		     * Start a forward search at the end of the line (unless
+		     * before the first line).
 		     * Start a backward search at the start of the line.
 		     * This makes sure we never match in the current
 		     * line, and can match anywhere in the
 		     * next/previous line.
 		     */
-		    if (c == '/')
+		    if (c == '/' && curwin->w_cursor.lnum > 0)
 			curwin->w_cursor.col = MAXCOL;
 		    else
 			curwin->w_cursor.col = 0;