[flang][runtime] Emit leading space before zero-length list-directed … (llvm#77835)

…character

Don't omit the leading space in list-directed output before a line
comprising only a zero-length character value.

Fixes llvm#77736.

Author: klausler

flang/runtime/io-stmt.cpp

@@ -698,9 +698,6 @@ void FormattedIoStatementState<Direction::Input>::GotChar(int n) {
 
 bool ListDirectedStatementState<Direction::Output>::EmitLeadingSpaceOrAdvance(
     IoStatementState &io, std::size_t length, bool isCharacter) {
-  if (length == 0) {
-    return true;
-  }
   const ConnectionState &connection{io.GetConnectionState()};
   int space{connection.positionInRecord == 0 ||
       !(isCharacter && lastWasUndelimitedCharacter())};