patch 8.2.0637: incsearch highlighting does not work for ":sort!"

Problem:    Incsearch highlighting does not work for ":sort!".
Solution:   Skip over the exclamation point. (closes #5983)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 18da926..7e92ec8 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -249,7 +249,9 @@
     }
     else if (STRNCMP(cmd, "sort", MAX(p - cmd, 3)) == 0)
     {
-	// skip over flags
+	// skip over ! and flags
+	if (*p == '!')
+	    p = skipwhite(p + 1);
 	while (ASCII_ISALPHA(*(p = skipwhite(p))))
 	    ++p;
 	if (*p == NUL)