prevent users from entering in empty table/field names.

frontend/src/admin/datamodel/components/database/ColumnItem.jsx

@@ -43,7 +43,12 @@ export default class Column extends Component {
     }
 
     onNameChange(event) {
-        this.updateProperty("display_name", event.target.value);
+        if (!_.isEmpty(event.target.value)) {
+            this.updateProperty("display_name", event.target.value);
+        } else {
+            // if the user set this to empty then simply reset it because that's not allowed!
+            event.target.value = this.props.field.display_name;
+        }
     }
 
     onDescriptionChange(event) {

frontend/src/admin/datamodel/components/database/MetadataTable.jsx

@@ -7,6 +7,7 @@ import SegmentsList from "./SegmentsList.jsx";
 import Input from "metabase/components/Input.jsx";
 import ProgressBar from "metabase/components/ProgressBar.jsx";
 
+import _ from "underscore";
 import cx from "classnames";
 
 export default class MetadataTable extends Component {
@@ -37,7 +38,12 @@ export default class MetadataTable extends Component {
     }
 
     onNameChange(event) {
-        this.updateProperty("display_name", event.target.value);
+        if (!_.isEmpty(event.target.value)) {
+            this.updateProperty("display_name", event.target.value);
+        } else {
+            // if the user set this to empty then simply reset it because that's not allowed!
+            event.target.value = this.props.tableMetadata.display_name;
+        }
     }
 
     onDescriptionChange(event) {

frontend/src/admin/datamodel/datamodel.controllers.js

@@ -128,13 +128,15 @@ function($scope, $route, $routeParams, $location, $q, $timeout, databases, Metab
         }
 
         score(table.description);
-        table.fields.forEach(function(field) {
-            score(field.description);
-            score(field.special_type);
-            if (field.special_type === "fk") {
-                score(field.target);
-            }
-        });
+        if (table.fields) {
+            table.fields.forEach(function(field) {
+                score(field.description);
+                score(field.special_type);
+                if (field.special_type === "fk") {
+                    score(field.target);
+                }
+            });
+        }
 
         return (completed / total);
     }