patch 8.0.1622: possible NULL pointer dereference

Problem:    Possible NULL pointer dereferencey. (Coverity)
Solution:   Reverse the check for a NULL pointer.

Author: brammool

src/quickfix.c

@@ -4256,7 +4256,7 @@ ex_vimgrep(exarg_T *eap)
 	goto theend;
     }
 
-    if (s != NULL && *s == NUL)
+    if (s == NULL || *s == NUL)
     {
 	/* Pattern is empty, use last search pattern. */
 	if (last_search_pat() == NULL)

src/version.c

@@ -766,6 +766,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1622,
 /**/
     1621,
 /**/