Don't block IO::Handle.get on TTYs after we reached EOF

Fixes RT#130086: https://rt.perl.org/Ticket/Display.html?id=130086

We don't block on non-TTYs nor do we block with other method such
as .read. While TTYs require an extra read to figure out when they
reach EOF, once we know we're at EOF, there's no point trying to
read again.

src/core/IO/Handle.pm

@@ -294,17 +294,19 @@ my class IO::Handle {
 
     method !get-line-slow-path() {
         my $line := Nil;
-        loop {
-            my $buf := self.read-internal(0x100000);
-            if $buf.elems {
-                $!decoder.add-bytes($buf);
-                $line := $!decoder.consume-line-chars(:$!chomp);
-                last if nqp::isconcrete($line);
-            }
-            else {
-                $line := $!decoder.consume-line-chars(:$!chomp, :eof)
-                    unless self.eof-internal && $!decoder.is-empty;
-                last;
+        unless self.eof-internal && $!decoder.is-empty {
+            loop {
+                my $buf := self.read-internal(0x100000);
+                if $buf.elems {
+                    $!decoder.add-bytes($buf);
+                    $line := $!decoder.consume-line-chars(:$!chomp);
+                    last if nqp::isconcrete($line);
+                }
+                else {
+                    $line := $!decoder.consume-line-chars(:$!chomp, :eof)
+                        unless self.eof-internal && $!decoder.is-empty;
+                    last;
+                }
             }
         }
         $line