Bug 1640686 - Add MIsObject instruction to the current block. r=iain

This assert is reached via MaybeSetImplicitlyUsed, so before bug 1640107 this problem might not have triggered the test suite at all.

Differential Revision: https://phabricator.services.mozilla.com/D76725

js/src/jit/WarpCacheIRTranspiler.cpp

@@ -1074,6 +1074,7 @@ bool WarpCacheIRTranspiler::emitIsObjectResult(ValOperandId inputId) {
     pushResult(constant(BooleanValue(true)));
   } else {
     auto* isObject = MIsObject::New(alloc(), value);
+    add(isObject);
     pushResult(isObject);
   }