Postgres update query complaining about text value when only NULL values are passed

Question

I am using Postgres 9.4.6.

Is there any reason why the below update query would execute successfully here:-

UPDATE "Predictions" 
    SET "userid" = c."userid",
        "Fixture_No" = c."Fixture_No",
        "Home_Side_Score" = c."Home_Side_Score",
        "Away_Side_Score" = c."Away_Side_Score"
    FROM (VALUES(288, 1, NULL, NULL),(288, 34, 1, 1))
    AS c("userid", "Fixture_No", "Home_Side_Score", "Away_Side_Score")
    WHERE "Predictions"."Fixture_No" = c."Fixture_No" AND "Predictions"."userid" = c."userid"

But with these values, the same query would fail with "ERROR: column "Home_Side_Score" is of type smallint but expression is of type text LINE 4: "Home_Side_Score" = c."Home_Side_Score",":

UPDATE "Predictions" 
    SET "userid" = c."userid",
        "Fixture_No" = c."Fixture_No",
        "Home_Side_Score" = c."Home_Side_Score",
        "Away_Side_Score" = c."Away_Side_Score"
    FROM (VALUES(288, 1, NULL, NULL),(288, 34, NULL, NULL))
    AS c("userid", "Fixture_No", "Home_Side_Score", "Away_Side_Score")
    WHERE "Predictions"."Fixture_No" = c."Fixture_No" AND "Predictions"."userid" = c."userid"

This doesn't make any sense as I am not trying to pass postgres text instead of an integer?

My predictions table is as follows:

CREATE TABLE "Predictions"
(
  userid smallint,
  "Fixture_No" smallint,
  "Home_Side_Score" smallint,
  "Away_Side_Score" smallint,
  "Prediction_ID" bigserial NOT NULL,
  "Joker_Played" boolean,
  "Result" integer NOT NULL DEFAULT 4,
  CONSTRAINT "Predictions_pkey" PRIMARY KEY ("Prediction_ID"),
  CONSTRAINT "Result_Type" FOREIGN KEY ("Result")
      REFERENCES "ResultTypes" ("Result_ID") MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)
WITH (
  OIDS=FALSE
);
ALTER TABLE "Predictions"
  OWNER TO bjlizgykrnyffr;