Cal. Ins. Code § 171

In case of such a provision or assignment, any act of the mortgagor, prior to the loss and which would otherwise avoid the insurance, will have the same effect, although the property is in the hands of the mortgagee; but any act which, under the contract of insurance, is to be performed by the mortgagor, may be performed by the mortgagee therein named, with the same effect as if it had been performed by the mortgagor.