No error messages when invalid combinations are raised

[stwalkerster]

Requesting production of certain items (like yellow science in a grey machine) or "5b" in a box instead of "b5" makes the calculation vanish without a trace. (Worthy of note - invalid combinations are still possible with some calculations)

An error message detailing the problem would be nice so the user can quickly see and fix the problem

[doomeer]

Indeed, that would be nice, good suggestion!