Make KotlinFacetSettingsProvider.getInstance() nullable

A module may not have a KotlinFacet.
It isn't correct to throw an exception in that case.

Original commit: 44b7a5cc36

jps/jps-common/src/org/jetbrains/kotlin/config/KotlinFacetSettings.kt

@@ -290,6 +290,8 @@ interface KotlinFacetSettingsProvider {
     fun getInitializedSettings(module: Module): KotlinFacetSettings
 
     companion object {
-        fun getInstance(project: Project) = ServiceManager.getService(project, KotlinFacetSettingsProvider::class.java)!!
+        fun getInstance(project: Project): KotlinFacetSettingsProvider? {
+            return ServiceManager.getService(project, KotlinFacetSettingsProvider::class.java)
+        }
     }
 }