Revert "Fix ASAN errors due adding offset to nullptr"

This reverts commit b933f42d51.

utf8proc.c

@@ -365,16 +365,9 @@ static utf8proc_ssize_t seqindex_write_char_decomposed(utf8proc_uint16_t seqinde
   for (; len >= 0; entry++, len--) {
     utf8proc_int32_t entry_cp = seqindex_decode_entry(&entry);
 
-    if (!dst){
-      written += utf8proc_decompose_char(entry_cp, dst,
-        (bufsize > written) ? (bufsize - written) : 0, options,
-      last_boundclass);
-    }else{
-      written += utf8proc_decompose_char(entry_cp, dst+written,
-        (bufsize > written) ? (bufsize - written) : 0, options,
-      last_boundclass);
-    }
-
+    written += utf8proc_decompose_char(entry_cp, dst+written,
+      (bufsize > written) ? (bufsize - written) : 0, options,
+    last_boundclass);
     if (written < 0) return UTF8PROC_ERROR_OVERFLOW;
   }
   return written;
@@ -557,18 +550,10 @@ UTF8PROC_DLLEXPORT utf8proc_ssize_t utf8proc_decompose_custom(
       if (custom_func != NULL) {
         uc = custom_func(uc, custom_data);   /* user-specified custom mapping */
       }
-      if (!buffer){
-        decomp_result = utf8proc_decompose_char(
-          uc, buffer, (bufsize > wpos) ? (bufsize - wpos) : 0, options,
-          &boundclass
-      ); 
-      }else{
-        decomp_result = utf8proc_decompose_char(
-          uc, buffer + wpos, (bufsize > wpos) ? (bufsize - wpos) : 0, options,
-          &boundclass
-        );
-      }
-
+      decomp_result = utf8proc_decompose_char(
+        uc, buffer + wpos, (bufsize > wpos) ? (bufsize - wpos) : 0, options,
+        &boundclass
+      );
       if (decomp_result < 0) return decomp_result;
       wpos += decomp_result;
       /* prohibiting integer overflows due to too long strings: */