make AddressSanitizer happy

vcfpp.h

@@ -1575,10 +1575,12 @@ class BcfWriter
     }
 
     /// write a string to a vcf line
-    void writeLine(std::string vcfline)
+    void writeLine(const std::string & vcfline)
     {
         if(!isHeaderWritten && !writeHeader()) throw std::runtime_error("could not write header\n");
-        kstring_t s = {vcfline.length(), vcfline.length(), &vcfline[0]}; // kstring
+        std::vector<char> str(vcfline.begin(), vcfline.end());
+        str.push_back('\0'); // don't forget string has no \0;
+        kstring_t s = {vcfline.length(), vcfline.length(), &str[0]}; // kstring
         ret = vcf_parse(&s, header.hdr, b.get());
         if(ret > 0) throw std::runtime_error("error parsing: " + vcfline + "\n");
         if(b->errcode == BCF_ERR_CTG_UNDEF)