This should not happen, if someone enters non-numeric value into the price field (my best guess what caused this from your error), and under normal circumstances it should not generate any warning. Mind you, a php "warning" is much serious event than a "notice", and should be taken care of [!]. However, I cannot trigger it on my end, core files takes care of this event properly. So, what could be wrong on your side - it's a puzzle, and without some details from your server logs, and setup, hard to reproduce and locate.
The answer itself might be in your free/bad host - 000webhost.
Turning off php reports from public on production site is, of course, a good [security] idea, but it does not help you in any way if you hide them entirely or ignore from your internal logs.