don't show "This alias is available to use" if an alias is not provided

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/components/views/elements/RoomAliasField.js

@@ -92,6 +92,7 @@ export default class RoomAliasField extends React.PureComponent {
                 invalid: () => _t("Please provide a room alias"),
             }, {
                 key: "taken",
+                skip: ({value}) => !value,
                 test: async ({value}) => {
                     if (!value) {
                         return true;

src/components/views/elements/Validation.js

@@ -51,9 +51,16 @@ export default function withValidation({ description, rules }) {
                 if (!rule.key || !rule.test) {
                     continue;
                 }
+
+                const data = { value, allowEmpty };
+
+                if (rule.skip && rule.skip.call(this, data)) {
+                    continue;
+                }
+
                 // We're setting `this` to whichever component holds the validation
                 // function. That allows rules to access the state of the component.
-                const ruleValid = await rule.test.call(this, { value, allowEmpty });
+                const ruleValid = await rule.test.call(this, data);
                 valid = valid && ruleValid;
                 if (ruleValid && rule.valid) {
                     // If the rule's result is valid and has text to show for