Move Null type to the Bottom in the VM (fixes #28025).

runtime/vm/precompiler.cc

Index: runtime/vm/precompiler.cc
diff --git a/runtime/vm/precompiler.cc b/runtime/vm/precompiler.cc
index ff691d1ab5709e3ba2f910b234eac1be1f0338ed..be0accfa44d1a1f9f35b1f259ac7baea2bcacd20 100644
--- a/runtime/vm/precompiler.cc
+++ b/runtime/vm/precompiler.cc
@@ -53,7 +53,7 @@ namespace dart {
 #define Z (zone())
 
 
-DEFINE_FLAG(bool, print_unique_targets, false, "Print unique dynaic targets");
+DEFINE_FLAG(bool, print_unique_targets, false, "Print unique dynamic targets");
 DEFINE_FLAG(bool, trace_precompiler, false, "Trace precompiler.");
 DEFINE_FLAG(
     int,
@@ -274,6 +274,7 @@ bool TypeRangeCache::InstanceOfHasClassRange(const AbstractType& type,
     if (!table->HasValidClassAt(cid)) continue;
     if (cid == kVoidCid) continue;
     if (cid == kDynamicCid) continue;
+    if (cid == kNullCid) continue;  // Instance is not at Bottom like Null type.
     cls = table->At(cid);
     if (cls.is_abstract()) continue;
     if (cls.is_patch()) continue;