Very quickly
You could use as an example in cell A18 in the Summary sheet
=IF(ISBLANK(Database!A6)," ",Database!A6)
However you need to be careful that you are trapping all errors or occurences that may occur in a cell. Such as
ISBLANK(value)
ISERR(value)
ISERROR(value)
ISLOGICAL(value)
ISNA(value)
ISNONTEXT(value)
ISNUMBER(value)
ISREF(value)
ISTEXT(value)
Value is the value you want tested. Value can be a blank (empty cell), error, logical, text, number, or reference value, or a name referring to any of these, that you want to test.
Each one of the above IS functions, returens True or False and you use the If statement to decide what will happen if what you are looking for if True or False.
If you are not familiar with using If statements, then you need to read up on those and get into nested IF statements