Revert "Displayio: Make imp.bidfloor optional (prebid#3959)"

This reverts commit 97bd74d.

adapters/displayio/displayio.go

@@ -37,18 +37,27 @@ func (adapter *adapter) MakeRequests(request *openrtb2.BidRequest, requestInfo *
 	for _, impression := range request.Imp {
 		var requestExt map[string]interface{}
 
-		if impression.BidFloorCur == "" || impression.BidFloor == 0 {
+		if impression.BidFloor == 0 {
+			errs = append(errs, &errortypes.BadInput{
+				Message: "BidFloor should be defined",
+			})
+			continue
+		}
+
+		if impression.BidFloorCur == "" {
 			impression.BidFloorCur = "USD"
-		} else if impression.BidFloorCur != "USD" {
+		}
+
+		if impression.BidFloorCur != "USD" {
 			convertedValue, err := requestInfo.ConvertCurrency(impression.BidFloor, impression.BidFloorCur, "USD")
 
 			if err != nil {
 				errs = append(errs, err)
 				continue
 			}
 
-			impression.BidFloor = convertedValue
 			impression.BidFloorCur = "USD"
+			impression.BidFloor = convertedValue
 		}
 
 		if len(impression.Ext) == 0 {

adapters/displayio/displayiotest/supplemental/missing-bidfloor.json

@@ -0,0 +1,35 @@
+{
+  "mockBidRequest": {
+    "id": "testid",
+    "imp": [
+      {
+        "id": "testimpid",
+        "banner": {
+          "format": [
+            {
+              "w": 300,
+              "h": 250
+            },
+            {
+              "w": 320,
+              "h": 50
+            }
+          ]
+        },
+        "ext": {
+          "bidder": {
+            "placementId": "1101",
+            "inventoryId": "1101",
+            "publisherId": "101"
+          }
+        }
+      }
+    ]
+  },
+  "expectedMakeRequestsErrors": [
+    {
+      "value": "BidFloor should be defined",
+      "comparison": "literal"
+    }
+  ]
+}