Fix NEGATIVE_RETURNS Coverity issue

lib/pkg_editor/src/pkg_editor.c:500:3:
  Type: Improper use of negative value (NEGATIVE_RETURNS)

lib/pkg_editor/src/pkg_editor.c:489:3:
  1. path: Condition "f == NULL", taking false branch. lib/pkg_editor/src/pkg_editor.c:496:3:
  2. negative_return_fn: Function "ftell(f)" returns a negative number. lib/pkg_editor/src/pkg_editor.c:496:3:
  3. assign: Assigning: "file_size" = "ftell(f)". lib/pkg_editor/src/pkg_editor.c:500:3:
  4. negative_returns: "file_size" is passed to a parameter that cannot be negative. lib/pkg_editor/src/pkg_editor.c:461:3:
  4.1. path: Condition "buf == NULL", taking false branch.
lib/pkg_editor/src/pkg_editor.c:459:60:
  4.2. sizet: "size" is a size_t parameter.

Author: IlanTruanovsky

lib/pkg_editor/src/pkg_editor.c

@@ -493,13 +493,13 @@ static char *read_file_into_buffer(struct acl_pkg_file *pkg,
 
   // get file size
   fseek(f, 0, SEEK_END);
-  long ftell_return = ftell(f);
+  const long ftell_return = ftell(f);
   if (ftell_return < 0) {
     fprintf(stderr, "Couldn't determine size of file %s\n", in_file);
     fclose(f);
     return NULL;
   }
-  file_size = ftell_return;
+  const size_t file_size = (size_t)ftell_return;
   rewind(f);
 
   // slurp the whole file into allocated buf