Ensure textSource is cleaned up if it isn't used

ext/mixed/js/text-scanner.js

@@ -299,11 +299,11 @@ class TextScanner {
             }
 
             const textSource = docRangeFromPoint(x, y, this.options.scanning.deepDomScan);
+            try {
                 if (this.textSourceCurrent !== null && this.textSourceCurrent.equals(textSource)) {
                     return;
                 }
 
-            try {
                 this.pendingLookup = true;
                 const result = await this.onSearchSource(textSource, cause);
                 if (result !== null) {