NSInternalInconsistencyException

2016-09-10 12:48:13.281 Friend[92304:1843372] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', 
reason: 'Invalid update: invalid number of rows in section 4. 
 The number of rows contained in an existing section after the update (0) must be equal to the number of rows 
contained in that section before the update (1), plus or minus the number of rows inserted or deleted from that 
section (0 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).'

　　是因为删完cell之后，数目不对