Remove empty, top-level, nodes in the Babel plugin

Looking at the *built* files you'll notice some lines containing nothing more than a semicolon. This is the result of (mostly top-level) `if`-statements, which include `PDFJSDev`-checks, that evalute to `false` during Babel parsing.

This has always annoyed me a bit, and looking at Babel plugin it seems that we can fix this simply by *removing* the relevant nodes.

external/builder/babel-plugin-pdfjs-preprocessor.mjs

@@ -84,11 +84,13 @@ function babelPluginPDFJSPreprocessor(babel, ctx) {
           if (t.isBooleanLiteral(node.test)) {
             // if (true) stmt1; => stmt1
             // if (false) stmt1; else stmt2; => stmt2
-            path.replaceWith(
+            if (node.test.value === true) {
-              node.test.value === true
+              path.replaceWith(node.consequent);
-                ? node.consequent
+            } else if (node.alternate) {
-                : node.alternate || t.emptyStatement()
+              path.replaceWith(node.alternate);
-            );
+            } else {
+              path.remove(node);
+            }
           }
         },
       },

external/builder/fixtures_esprima/ifs-expected.js

@@ -7,11 +7,12 @@ if ('test') {
 {
   "1";
 }
-;
 {
   "2";
 }
-;
 if ('1') {
   "1";
 }
+function f1() {
+  "1";
+}

external/builder/fixtures_esprima/ifs.js

@@ -23,3 +23,12 @@ if (true && false) {
 if (true && false || '1') {
   "1";
 }
+
+function f1() {
+  if (true) {
+    "1";
+  }
+  if (false) {
+    "2";
+  }
+}