fixes #8961

lib/system/sysio.nim

@@ -161,7 +161,7 @@ proc readLine(f: File, line: var TaintedString): bool =
       var last = cast[ByteAddress](m) - cast[ByteAddress](addr line.string[0])
       if last > 0 and line.string[last-1] == '\c':
         line.string.setLen(last-1)
-        return fgetsSuccess
+        return last > 1 or fgetsSuccess
         # We have to distinguish between two possible cases:
         # \0\l\0 => line ending in a null character.
         # \0\l\l => last line without newline, null was put there by fgets.
@@ -169,7 +169,7 @@ proc readLine(f: File, line: var TaintedString): bool =
         if last < pos + sp - 1 and line.string[last+1] != '\0':
           dec last
       line.string.setLen(last)
-      return fgetsSuccess
+      return last > 0 or fgetsSuccess
     else:
       # fgets will have inserted a null byte at the end of the string.
       dec sp