Under the old compiler, the CONVERSION (or CONV) condition would be raised if a character string consisting of one or more blanks (and nothing else) was assigned to a numeric variable. However if a varying character string of length zero was assigned to a numeric variable, CONVERSION would not have been raised (even though a zero-length character string compares equal to character string consisting only of blanks).
Under the new compiler, the CONVERSION condition will not be raised by the assignment to a numeric variable of any character string that would compare equal to a blank string.