util-ja3: fix AddressSanitizer heap-buffer-overflow

No resizing is done in Ja3BufferResizeIfFull() when the buffer is
empty. This leads to a potential overflow when this happens, since
a ',' is appended even when the buffer is empty.

Bug #2762

src/util-ja3.c

@@ -77,10 +77,6 @@ static int Ja3BufferResizeIfFull(JA3Buffer *buffer, uint32_t len)
 {
     DEBUG_VALIDATE_BUG_ON(buffer == NULL);
 
-    if (len == 0) {
-        return 0;
-    }
-
     while (buffer->used + len + 2 > buffer->size)
     {
         buffer->size *= 2;