Prevent accidentally overriding the `error` function in the `commonobj` messageHandler in api.js (issue 7232)

This naming issue has been present since PR 3529, but at least I cannot find any issues/bugs that seem to have been caused by it, which is good.

The patch also removes an unnecessary `else` branch, since an already existing `break` means that it's redundant.

Fixes 7232.

src/display/api.js

@@ -1486,13 +1486,12 @@ var WorkerTransport = (function WorkerTransportClosure() {
           case 'Font':
             var exportedData = data[2];
 
-            var font;
             if ('error' in exportedData) {
-              var error = exportedData.error;
-              warn('Error during font loading: ' + error);
-              this.commonObjs.resolve(id, error);
+              var exportedError = exportedData.error;
+              warn('Error during font loading: ' + exportedError);
+              this.commonObjs.resolve(id, exportedError);
               break;
-            } else {
+            }
             var fontRegistry = null;
             if (getDefaultSetting('pdfBug') && globalScope.FontInspector &&
                 globalScope['FontInspector'].enabled) {
@@ -1502,12 +1501,11 @@ var WorkerTransport = (function WorkerTransportClosure() {
                 }
               };
             }
-              font = new FontFaceObject(exportedData, {
+            var font = new FontFaceObject(exportedData, {
               isEvalSuported: getDefaultSetting('isEvalSupported'),
               disableFontFace: getDefaultSetting('disableFontFace'),
               fontRegistry: fontRegistry
             });
-            }
 
             this.fontLoader.bind(
               [font],