PVS-Studio warning V528 for Miranda IM

static char *_skipblank(char * str)
{
  char * endstr=str+strlen(str);
  while ((*str==' ' || *str=='\t') && str!='\0') str++;
  while ((*endstr==' ' || *endstr=='\t') &&
         endstr!='\0' && endstr<str)
    endstr--;
  ...
}

This code is a candidate for access violation: the '*' pointer dereferencing is missing twice.

This suspicious code was found in Miranda IM project by PVS-Studio static code analyzer.
Warning message is:
V528 It is odd that pointer to 'char' type is compared with the '\0' value. Probably meant: *str != '\0'.  clist_modern  modern_skinbutton.cpp  282

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