don't set NewRemoved values as empty strings

NewRemoved diff values were somtimes left in maps and lists.

terraform/diff.go

@@ -699,14 +699,6 @@ func (d *InstanceDiff) applySingleAttrDiff(path []string, attrs map[string]strin
 		return result, nil
 	}
 
-	if diff.Old == diff.New && diff.New == "" {
-		// this can only be a valid empty string
-		if attrSchema.Type == cty.String {
-			result[attr] = ""
-		}
-		return result, nil
-	}
-
 	// check for missmatched diff values
 	if exists &&
 		old != diff.Old &&
@@ -715,13 +707,21 @@ func (d *InstanceDiff) applySingleAttrDiff(path []string, attrs map[string]strin
 		return result, fmt.Errorf("diff apply conflict for %s: diff expects %q, but prior value has %q", attr, diff.Old, old)
 	}
 
-	if attrSchema.Computed && diff.NewComputed {
-		result[attr] = config.UnknownVariableValue
+	if diff.NewRemoved {
+		// don't set anything in the new value
+		return map[string]string{}, nil
+	}
+
+	if diff.Old == diff.New && diff.New == "" {
+		// this can only be a valid empty string
+		if attrSchema.Type == cty.String {
+			result[attr] = ""
+		}
 		return result, nil
 	}
 
-	if diff.NewRemoved {
-		// don't set anything in the new value
+	if attrSchema.Computed && diff.NewComputed {
+		result[attr] = config.UnknownVariableValue
 		return result, nil
 	}
 
@@ -863,8 +863,10 @@ func (d *InstanceDiff) applyCollectionDiff(path []string, attrs map[string]strin
 		}
 	}
 
-	// Fill in the count value if it was missing for some reason:
-	if result[countKey] == "" {
+	// Fill in the count value if it wasn't present in the diff for some reason,
+	// or if there is no count at all.
+	_, countDiff := d.Attributes[countKey]
+	if result[countKey] == "" || (!countDiff && len(keys) != len(result)) {
 		result[countKey] = countFlatmapContainerValues(countKey, result)
 	}