patch 8.0.1512: warning for possibly using NULL pointer

Problem:    Warning for possibly using NULL pointer. (Coverity)
Solution:   Skip using the pointer if it's NULL.

Author: brammool

src/ex_cmds.c

@@ -6918,7 +6918,7 @@ fix_help_buffer(void)
 		copy_option_part(&p, NameBuff, MAXPATHL, ",");
 		mustfree = FALSE;
 		rt = vim_getenv((char_u *)"VIMRUNTIME", &mustfree);
-		if (fullpathcmp(rt, NameBuff, FALSE) != FPC_SAME)
+		if (rt != NULL && fullpathcmp(rt, NameBuff, FALSE) != FPC_SAME)
 		{
 		    int		fcount;
 		    char_u	**fnames;

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1512,
 /**/
     1511,
 /**/