[Synthetics] Fix ping heatmap payload (elastic#195107)

## Summary

We addressed elastic#180076 recently
with these two PRs:

- elastic#184177
- elastic#192508

We were seeing a strange error that was difficult to repro, so we put in
a best-effort patch that was still ineffective. The reason this issue
happens is because in the code it's possible to divide by 0, which
yields a value of `Infinity`, which at some point causes our interval
value supplied to the server route to be an empty string.

This patch will make it so that we never pass a value of 0 to be used in
the calculation of bucket sizes in this hook.

(cherry picked from commit 560d561)

x-pack/plugins/observability_solution/synthetics/public/apps/synthetics/components/monitor_details/monitor_status/use_monitor_status_data.ts

@@ -93,7 +93,7 @@ export const useMonitorStatusData = ({ from, to, initialSizeRef }: Props) => {
 
   useDebounce(
     async () => {
-      setDebouncedCount(binsAvailableByWidth);
+      setDebouncedCount(binsAvailableByWidth === 0 ? null : binsAvailableByWidth);
     },
     500,
     [binsAvailableByWidth]