PVS/V1032: pointer cast to a more strictly aligned type

Rework-of: ea7491586f
Helped-by: Björn Linse <bjorn.linse@gmail.com>

- The old (Vim) use of (char_u **)"" before ea7491586f is garbage,
  which hints that this value was never used.
- The necessary condition is next to the NULL assigmnent, the pointer
  would only be started to be accessed, if the length assignment next to
  it is also changed.

src/nvim/ex_cmds.c

@@ -4895,7 +4895,7 @@ int find_help_tags(const char_u *arg, int *num_matches, char_u ***matches,
     }
   }
 
-  *matches = &vim_emptystr;
+  *matches = NULL;
   *num_matches = 0;
   int flags = TAG_HELP | TAG_REGEXP | TAG_NAMES | TAG_VERBOSE;
   if (keep_lang) {

src/nvim/ex_getln.c

@@ -4702,7 +4702,7 @@ ExpandFromContext (
     return ret;
   }
 
-  *file = &vim_emptystr;
+  *file = NULL;
   *num_file = 0;
   if (xp->xp_context == EXPAND_HELP) {
     /* With an empty argument we would get all the help tags, which is

src/nvim/globals.h

@@ -1081,9 +1081,6 @@ EXTERN FILE *time_fd INIT(= NULL);  /* where to write startup timing */
 // can't do anything useful with the value.  Assign to this variable to avoid
 // the warning.
 EXTERN int vim_ignored;
-// Use this to avoid PVS warning V1032 for code like this:
-//    *foo = (char_u **)"";
-EXTERN char_u *vim_emptystr INIT(= (char_u *)"");
 
 // Start a msgpack-rpc channel over stdin/stdout.
 EXTERN bool embedded_mode INIT(= false);

src/nvim/path.c

@@ -1267,7 +1267,7 @@ int gen_expand_wildcards(int num_pat, char_u **pat, int *num_file,
   }
 
   *num_file = ga.ga_len;
-  *file = (ga.ga_data != NULL) ? (char_u **)ga.ga_data : &vim_emptystr;
+  *file = (ga.ga_data != NULL) ? (char_u **)ga.ga_data : NULL;
 
   recursive = false;