Does the pursing of the lips when pronouncing the "M" in "An'amta" with a two-count ghunnah render the recitation invalid, and consequently the prayer invalid?

The letter Meem (م) is pronounced by closing the lips. The ghunnah (nasalization) is not inherent to it, except when it is a mushaddad (doubled) letter or when it is saakin (vowel-less) followed by a Baa (ب) or another Meem (م). The Meem in "an'amta" (أنعمت) is saakin, and it is not followed by a Baa or a Meem. Therefore, there is no ghunnah in it. Pronouncing it with ghunnah is a minor, hidden لحن (error) that does not invalidate the prayer.