Convert <undefined> to NaN or leave blank

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MW_samples_Mathworks.csv

When reading in a table, columns with blank cells are read in as type "cell". I need to convert those columns to numeric, with blank cells being NaN or left empty. In previous version of Matlab, I could convert them to "categorical", but with the Matlab update to 2022b, the blank cells are listed as <undefined> after conversion. How can I change these undefined values to NaN or leave them empty, or just change the black cell values to NaN?. I've listed my current code and have attached a sample of the data. Im particularly concerned about Var60:Var80. The top image is what the data looks like prior to converting to categorical. The second image is what it looks like after converting it to categorical.

Mo=readtable('MW_samples_Mathworks.csv');
Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.
Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.
Mo(1:3,:)=[];
Mo = removevars(Mo,{'Stevens','DATASETCOMPLETE','endTime','USGS','Nozzle','Transits','Tagline','Water','Sample'...
    'Sampling','Pump','Pump_1','Cross_section','Var30','Laboratory_determinedValues','Var32','Var33','Var34','Var35'...
    'Var36','Var37','Var38','Var39','Var40','Var41','Var42','Var43','Var44','Var45','Var46','Var47','Var48','Var49','Var50','Var51'...
    'Var52','Var53','Var54','Var55','Var56','Var57','Var58','ColorOf','SpecificConductance','TDS','AirTemp','WaterTemp',...
    'Concentration','Grain_size','LabNotes','MethodUsedForDetermining','x95__confidence_level','x95__confidence_level_1',...
    'x95__confidence_level_2','x95__confidence_level_3','x95__confidence_level_4','x95__confidence_level_5','x95__confidence_level_6'...
    'x95__confidence_level_7','x95__confidence_level_8','x95__confidence_level_9','Var101','Var102','CorrectionForNegative'});
Mo = convertvars(Mo,@iscellstr,'categorical');