Size method in if expression inside randomize...with (wrong warning)

Warning message does not contain an expression that causes the problem:
%Warning-CONSTRAINTIGN: /path/riscv-dv/src/riscv_instr_stream.sv:286:51: Unsupported: randomizing this expression, treating as state
                        /path/riscv-dv/src/riscv_instr_pkg.sv:1589:1: ... note: In file included from 'riscv_instr_pkg.sv'
                        ... For warning description see https://verilator.org/warn/CONSTRAINTIGN?v=5.031
                        ... Use "/* verilator lint_off CONSTRAINTIGN */" and lint_on around source to disable this message.

Signed-off-by: Ryszard Rozak <[email protected]>

src/riscv_instr_stream.sv

@@ -255,7 +255,7 @@ class riscv_rand_instr_stream extends riscv_instr_stream;
 
   function void randomize_gpr(riscv_instr instr);
     `DV_CHECK_RANDOMIZE_WITH_FATAL(instr,
-      if (avail_regs.size() > 0) {
+      if (1 > 0) {
         if (has_rs1) {
           rs1 inside {avail_regs};
         }