Fortran: Fix ICE caused by missing error for untyped symbol [PR103258]
The bit on a symbol to mark that it had already been diagnosed as
lacking a type was getting set even when the error was suppressed or
discarded, specifically when doing early resolution on a character
length expression to see if it can be constant-folded. Explicitly
suppress errors before doing that, then check whether they are
suppressed before setting the bit.