In this passage, the 1874 RLDS edition dropped the definite article the from the phrase “with all the energy of heart”. This loss of the the was undoubtedly accidental since there is definitely nothing wrong with its use here. The 1908 RLDS edition restored the correct phraseology here in Moroni 7:48.
Summary: Maintain in Moroni 7:48 the definite article the in the phrase “with all the energy of heart”, the reading of the earliest extant text.