Add internal utility for zeroing int vectors.

PiperOrigin-RevId: 562608956
Change-Id: I25ff1bbf9abf8fe2a636ed1d728d10ae862e04c9

src/engine/engine_util_misc.c

@@ -1207,6 +1207,15 @@ int mju_isZero(mjtNum* vec, int n) {
 
 
 
+// set integer vector to 0
+void mju_zeroInt(int* res, int n) {
+  if (n > 0) {
+    memset(res, 0, n*sizeof(int));
+  }
+}
+
+
+
 // standard normal random number generator (optional second number)
 mjtNum mju_standardNormal(mjtNum* num2) {
   const mjtNum scale = 2.0/((mjtNum)RAND_MAX);