Minor. Change CompilationException parameter to @Nullable

A lot of call sites actally pass null as an element,
so it's better to fail with original stack-trace instead of NPE
caused by nullability check

compiler/cli/src/org/jetbrains/kotlin/cli/common/messages/MessageUtil.java

@@ -31,7 +31,8 @@ public class MessageUtil {
     private MessageUtil() {}
 
     @NotNull
-    public static CompilerMessageLocation psiElementToMessageLocation(@NotNull PsiElement element) {
+    public static CompilerMessageLocation psiElementToMessageLocation(@Nullable PsiElement element) {
+        if (element == null) return CompilerMessageLocation.NO_LOCATION;
         PsiFile file = element.getContainingFile();
         return psiFileToMessageLocation(file, "<no path>", DiagnosticUtils.getLineAndColumnInPsiFile(file, element.getTextRange()));
     }