fix(@ngtools/webpack): skip transforming empty inline styles in Webpack JIT compilations

Empty styles break the Webpack resource loader / PostCSS and generate an error. Fortunately there's no work to be done there, so we can just skip it and leave the empty string.

(cherry picked from commit 7b02161)

Author: dgp1130

packages/ngtools/webpack/src/transformers/replace_resources.ts

@@ -236,6 +236,11 @@ function transformInlineStyleLiteral(
     return node;
   }
 
+  // Don't transform empty strings as PostCSS will choke on them. No work to do anyways.
+  if (node.text === '') {
+    return node;
+  }
+
   if (!isInlineStyle) {
     const url = getResourceUrl(node);