[2.1.0] Checkmk Werk 16300 created: Revert werk #16150 and fix <tt>IndexError: boolean index did not match indexed array along dimension 0<tt> in forecast graphs

Title: Revert werk #16150 and fix <tt>IndexError: boolean index did not match indexed array along dimension 0<tt> in forecast graphs Class: fix Compatible: compat Component: metrics Date: 1700760668 Edition: cee Level: 1 Version: 2.1.0p37 This change reverts werk #16150, since this werk made forecast graphs basically unusable. Furthermore, this change fixes the error mentioned above. This error occurred when computing a forecast based on constant and incomplete input data.