fix: Rspack cssParser will parse failed when url(' ') (#8824)

fix: parsing process for handling strings with multiple spaces

Co-authored-by: bobihuang <[email protected]>

crates/rspack_plugin_css/src/parser_and_generator/mod.rs

@@ -164,7 +164,7 @@ impl ParserAndGenerator for CssParserAndGenerator {
           range,
           kind,
         } => {
-          if request.is_empty() {
+          if request.trim().is_empty() {
             continue;
           }
           let request = replace_module_request_prefix(

packages/rspack-test-tools/tests/builtinCases/plugin-css/simple-url/__snapshots__/output.snap.txt

@@ -0,0 +1,7 @@
+```css title=main.css
+body {
+  background: red url('    ');
+}
+
+
+```

packages/rspack-test-tools/tests/builtinCases/plugin-css/simple-url/index.js

@@ -0,0 +1 @@
+import "./style.css";

packages/rspack-test-tools/tests/builtinCases/plugin-css/simple-url/style.css

@@ -0,0 +1,3 @@
+body {
+  background: red url('    ');
+}