What is the ruling regarding a master who apostatizes after designating a slave as Mudabbar (to be freed upon master's death)?

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According to the established madhhab, if the master of a Mudabbar apostatizes, the designation remains contingent (mawquf). If the master returns to Islam, the designation remains in effect because the master's ownership was never truly extinguished. However, if the master dies or is killed while in a state of apostasy, the slave is not freed because the master's ownership is deemed to have ceased upon apostasy. Abu Bakr suggested that, based on Imam Ahmad's position, apostasy invalidates the designation (Tadbir), requiring a new designation upon returning to Islam. Al-Shafi'i holds that the designation remains valid and the slave is freed upon the master's death, analogizing it to a sale or gift made before apostasy, which depends on the ruling regarding the property of an apostate.