Werk #8877: Historic metrics painter: Prevent empty views, improve error handling

Component	User interface
Title	Historic metrics painter: Prevent empty views, improve error handling
Date	Aug 23, 2019
Level	Trivial Change
Class	Bug Fix
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	2.0.0i1 Checkmk Enterprise (CEE), Checkmk MSP (CME) 1.6.0b8 Checkmk Enterprise (CEE), Checkmk MSP (CME)

When adding the "historic metrics painter" to a view, this could result in empty views when none of the fetched row could satisfy the required metrics. Instead of filtering out all rows, we now leave the rows untouched and show an error message in the historic metrics painter.

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