8375657: RISC-V: Need to check size in SharedRuntime::is_wide_vector

Reviewed-by: fjiang, fyang

src/hotspot/cpu/riscv/sharedRuntime_riscv.cpp

@@ -213,7 +213,7 @@ void RegisterSaver::restore_live_registers(MacroAssembler* masm) {
 // Is vector's size (in bytes) bigger than a size saved by default?
 // riscv does not ovlerlay the floating-point registers on vector registers like aarch64.
 bool SharedRuntime::is_wide_vector(int size) {
-  return UseRVV;
+  return UseRVV && size > 0;
 }
 
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