I'm trying to find a minimal adequate model using AIC in R. I keep getting the following error: Error in step(model) : number of rows in use has changed: remove missing values?

My data:

data<-structure(list(ID = c(1L, 2L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 
12L, 13L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 21L, 22L, 23L, 24L, 
25L, 27L, 28L, 29L, 30L, 31L, 33L, 34L, 35L, 37L, 38L, 39L, 40L, 
41L, 42L, 43L, 44L, 45L, 46L, 47L, 48L, 49L, 50L, 51L, 52L, 53L, 
54L, 55L, 56L, 57L, 58L, 59L, 60L, 61L, 62L, 63L, 64L, 65L, 66L, 
67L, 68L, 69L, 70L, 71L, 72L, 73L, 74L, 75L, 76L, 77L, 78L, 79L, 
80L, 81L, 82L, 83L, 84L, 85L, 86L, 87L, 88L, 89L, 90L, 91L, 92L, 
93L, 94L, 95L, 96L, 98L, 99L, 100L, 102L, 103L, 104L, 105L, 106L, 
107L, 108L, 109L, 111L, 112L, 113L, 114L, 115L, 116L, 117L, 118L, 
119L, 120L, 121L, 122L, 123L), QnWeight_initial = c(158L, 165L, 
137L, 129L, 155L, 150L, 119L, 153L, 137L, 153L, 158L, 163L, 159L, 
151L, 145L, 144L, 157L, 154L, 144L, 133L, 148L, 151L, 151L, 147L, 
158L, 178L, 164L, 166L, 134L, 151L, 151L, 157L, 148L, 142L, 127L, 
179L, 162L, 142L, 150L, 151L, 153L, 163L, 155L, 163L, 170L, 159L, 
151L, 149L, 154L, 129L, 165L, 128L, 160L, 162L, 134L, 145L, 147L, 
148L, 160L, 165L, 131L, 155L, 169L, 143L, 123L, 153L, 151L, 152L, 
146L, 157L, 154L, 144L, 163L, 153L, 141L, 133L, 167L, 151L, 155L, 
142L, 164L, 158L, 141L, 179L, 146L, 149L, 164L, 156L, 153L, 132L, 
159L, 139L, 139L, 163L, 160L, 155L, 163L, 154L, 135L, 152L, 149L, 
143L, 140L, 160L, 150L, 143L, 160L, 159L, 144L, 169L, 152L, 146L, 
152L, 148L, 138L, 152L), QnWeight_initial_mg = c(15.8, 16.5, 
13.7, 12.9, 15.5, 15, 11.9, 15.3, 13.7, 15.3, 15.8, 16.3, 15.9, 
15.1, 14.5, 14.4, 15.7, 15.4, 14.4, 13.3, 14.8, 15.1, 15.1, 14.7, 
15.8, 17.8, 16.4, 16.6, 13.4, 15.1, 15.1, 15.7, 14.8, 14.2, 12.7, 
17.9, 16.2, 14.2, 15, 15.1, 15.3, 16.3, 15.5, 16.3, 17, 15.9, 
15.1, 14.9, 15.4, 12.9, 16.5, 12.8, 16, 16.2, 13.4, 14.5, 14.7, 
14.8, 16, 16.5, 13.1, 15.5, 16.9, 14.3, 12.3, 15.3
r linear-regression
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