Fix bug in generic case for gen_checktype

When checking for T_HASH, which is Qnil and when the type check succeeds
we were outputting to the stack a Qnil instead of a Qtrue.

bootstraptest/test_yjit.rb

@@ -1154,6 +1154,26 @@ assert_equal '7', %q{
   foo(5,2)
 }
 
+# test pattern matching
+assert_equal '[:ok, :ok]', %q{
+  class C
+    def destructure_keys
+      {}
+    end
+  end
+
+  pattern_match = ->(i) do
+    case i
+    in a: 0
+      :ng
+    else
+      :ok
+    end
+  end
+
+  [{}, C.new].map(&pattern_match)
+}
+
 # Call to object with singleton
 assert_equal '123', %q{
   obj = Object.new

yjit_codegen.c

@@ -1421,6 +1421,7 @@ gen_checktype(jitstate_t* jit, ctx_t* ctx)
         mov(cb, REG0, mem_opnd(64, REG0, offsetof(struct RBasic, flags)));
         and(cb, REG0, imm_opnd(RUBY_T_MASK));
         cmp(cb, REG0, imm_opnd(type_val));
+        mov(cb, REG0, imm_opnd(Qtrue));
         mov(cb, REG1, imm_opnd(Qfalse));
         cmovne(cb, REG0, REG1);