Throw correct exception in HAL_getJoystickAxes/POVs JNI (#1336)

Was incorrectly not returning immediately after throwing the exception.

Also add more detail to exception.

hal/src/main/native/cpp/jni/HALUtil.cpp

@@ -206,7 +206,7 @@ void ReportCANError(JNIEnv* env, int32_t status, int message_id) {
   }
 }
 
-void ThrowIllegalArgumentException(JNIEnv* env, const char* msg) {
+void ThrowIllegalArgumentException(JNIEnv* env, wpi::StringRef msg) {
   illegalArgExCls.Throw(env, msg);
 }