Handle a case when a module group name is empty in Gradle Plugin.

And change error reporting to warning for unknown resource type

gradle-plugins/compose/src/main/kotlin/org/jetbrains/compose/resources/GenerateResClassTask.kt

@@ -79,7 +79,7 @@ abstract class GenerateResClassTask : DefaultTask() {
             val type = try {
                 ResourceType.fromString(typeString)
             } catch (e: Exception) {
-                logger.error("e: Error: $path", e)
+                logger.warn("w: Skip file: $path\n${e.message}")
                 return null
             }
             listOf(ResourceItem(type, qualifiers, file.nameWithoutExtension.asUnderscoredIdentifier(), path))
@@ -100,4 +100,4 @@ abstract class GenerateResClassTask : DefaultTask() {
 internal fun String.asUnderscoredIdentifier(): String =
     lowercase()
         .replace('-', '_')
-        .let { if (it.first().isDigit()) "_$it" else it }
+        .let { if (it.isNotEmpty() && it.first().isDigit()) "_$it" else it }

gradle-plugins/compose/src/test/kotlin/org/jetbrains/compose/test/tests/integration/ResourcesTest.kt

@@ -17,7 +17,7 @@ class ResourcesTest : GradlePluginTestBase() {
                 file("expected/Res.kt")
             )
             check.logContains("""
-                java.lang.IllegalStateException: Unknown resource type: ignored
+                Unknown resource type: ignored
             """.trimIndent())
         }