fix(pack): invalid css url request should throw waring instead of error

crates/pack-tests/tests/snapshot/style/invalid_pseudo_class/input/index.less

@@ -23,4 +23,12 @@ form[id='step1'] {
 .displayName {
     color: var(rgba(4, 15, 36, 0.85));
     margin-bottom: 12px;
+}
+
+.layoutContainer {
+    background-image: url('');
+}
+
+.layoutContainer2 {
+    background-image: url(<path-to-image>) lightgray 50% / cover no-repeat
 }

crates/pack-tests/tests/snapshot/style/invalid_pseudo_class/issues/__l___Module not found____c__ Can't resolve __c_''-791687.txt

@@ -0,0 +1,26 @@
+warning - [resolve] /style/invalid_pseudo_class/input/index.less.css:30:4  Module not found: Can't resolve ''
+
+      26 |     margin-bottom: 12px;
+      27 | }
+      28 | 
+      29 | .layoutContainer {
+         +     v
+      30 +     background-image: url('');
+         +     ^
+      31 | }
+      32 | 
+      33 | .layoutContainer2 {
+      34 |     background-image: url(<path-to-image>) lightgray 50% / cover no-repeat
+
+
+
+  | It was not possible to find the requested file.
+  | Parsed request as written in source code: empty
+  | Path where resolving has started: [project]/style/invalid_pseudo_class/input/index.less.css
+  | Type of request: url request
+  | 
+  Import trace:
+    Browser:
+      ./style/invalid_pseudo_class/input/index.less.css
+      ./style/invalid_pseudo_class/input/index.less
+      ./style/invalid_pseudo_class/input/index.ts

crates/pack-tests/tests/snapshot/style/invalid_pseudo_class/issues/__l___Module not found____c__ Can't resolve __c_'<-03e98d.txt

@@ -0,0 +1,23 @@
+warning - [resolve] /style/invalid_pseudo_class/input/index.less.css:34:4  Module not found: Can't resolve '<path-to-image>'
+
+      30 |     background-image: url('');
+      31 | }
+      32 | 
+      33 | .layoutContainer2 {
+         +     v
+      34 +     background-image: url(<path-to-image>) lightgray 50% / cover no-repeat
+         +     ^
+      35 | }
+
+
+
+  | It was not possible to find the requested file.
+  | Parsed request as written in source code: module "'<path-to-image>'"
+  | Path where resolving has started: [project]/style/invalid_pseudo_class/input/index.less.css
+  | Type of request: url request
+  | 
+  Import trace:
+    Browser:
+      ./style/invalid_pseudo_class/input/index.less.css
+      ./style/invalid_pseudo_class/input/index.less
+      ./style/invalid_pseudo_class/input/index.ts