large image can not be uploaded because localstorage quota is reached

the quota in chrome is 5Mo

current localstorage mem footprint:

1,1Mo for investigations
2,7Mo for scientistInstrumentInvestigations
-----
total ~ 3.8Mo, 

so 1,2Mo left for the rest including img blob in the logbook. Note that the blob is present temporarily in the localstorage until the image has been uploaded successfully.

the console gives :

when the user clicks the save button to save his new event containing only this large imiage the result is