What is the test for reversal of a jury instruction that omits an element of an offence?

"'"'[A] defendant has a constitutional right to have the jury determine every material issue presented by the evidence [and] ... an erroneous failure to instruct on a lesser included offense constitutes a denial of that right ....' [Citation.]"' [Citation.]" (People v. Prince (2007) 40 Cal.4th 1179, 1264.) "A jury instruction that omits an element of an offense requires reversal unless the error was harmless beyond a reasonable doubt. [Citation.] However, if no rational jury could have found the missing element unproven, the error is harmless beyond a reasonable doubt." (People v. Nicholson (2004)

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