Fixed unsaved changes modal showing after focus/blur of tag and member fields

no issue

- the inputs in tag/member settings are now two-way bound which means that a `null` or `undefined` value can become `""` when a field is focused/blurred due to inputs only working on strings
- if a `null` or `undefined` property value becomes `""` Ember Data will treat that as a dirty property and that will in turn trigger the unsaved changes modal when leaving the tag/member details screens
- this change strengthens our `_saveXProperty` private controller methods to skip any changes between "falsy" property values unless the new value is explicitly `false`

ghost/admin/app/controllers/member.js

@@ -116,7 +116,17 @@ export default Controller.extend({
     }),
 
     _saveMemberProperty(propKey, newValue) {
-        let member = this.member;
-        member.set(propKey, newValue);
+        let currentValue = this.member.get(propKey);
+
+        if (newValue) {
+            newValue = newValue.trim();
+        }
+
+        // avoid modifying empty values and triggering inadvertant unsaved changes modals
+        if (newValue !== false && !newValue && !currentValue) {
+            return;
+        }
+
+        this.member.set(propKey, newValue);
     }
 });

ghost/admin/app/controllers/tag.js

@@ -114,6 +114,11 @@ export default Controller.extend({
             newValue = newValue.trim();
         }
 
+        // avoid modifying empty values and triggering inadvertant unsaved changes modals
+        if (newValue !== false && !newValue && !currentValue) {
+            return;
+        }
+
         // Quit if there was no change
         if (newValue === currentValue) {
             return;
@@ -122,7 +127,7 @@ export default Controller.extend({
         tag.set(propKey, newValue);
 
         // Generate slug based on name for new tag when empty
-        if (propKey === 'name' && !tag.get('slug') && tag.isNew) {
+        if (propKey === 'name' && !tag.slug && tag.isNew) {
             let slugValue = slugify(newValue);
             if (/^#/.test(newValue)) {
                 slugValue = 'hash-' + slugValue;