Bug 1375404 - Remove bogus assert, r=jandem.

js/src/jit-test/tests/ion/bug1375404.js

@@ -0,0 +1,10 @@
+// |jit-test| error:ReferenceError
+
+Object.prototype.f = 42;
+var T = TypedObject;
+var ObjectStruct = new T.StructType({f: T.Object});
+Object.prototype.f = 42;
+var o = new ObjectStruct();
+evaluate(`
+  o.f %= p;
+`);

js/src/jit/IonBuilder.cpp

@@ -7243,7 +7243,6 @@ IonBuilder::ensureDefiniteType(MDefinition* def, MIRType definiteType)
                 replace = MToDouble::New(alloc(), def);
                 break;
             }
-            MOZ_ASSERT(def->type() == definiteType);
             return def;
         }
         replace = MUnbox::New(alloc(), def, definiteType, MUnbox::Infallible);