Error: Unable to get property type of undefined or null references

[ashley95e]

Can anyone tell me why I keep getting this Obscure message- its the same data that worked 2 days ago without issue. I combed through the data- once again this is Excel data mainly dates- Ive been careful to stick to a generic Excel spreadsheet mode. 

[ashley95e]

I believe Ive found the cause of the error issue

It appears Excel blank cells in a column with numbers typed  "General" for the column produce these errors  

"Unable to get property type of undefined or null references"

At least thats what I got from Access's imported error table - once I Data-Typed the data in the column as "Number" the table uploaded into BI quietly. with over 10,858 rows in this table (..and this is test data) it was easily over looked