Report error about invalid if as expression on the if keyword

#KT-14633 Fixed

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProvider.kt

@@ -717,7 +717,7 @@ class ControlFlowInformationProvider private constructor(
                 val elseExpression = element.`else`
 
                 if (thenExpression == null || elseExpression == null) {
-                    trace.report(INVALID_IF_AS_EXPRESSION.on(element))
+                    trace.report(INVALID_IF_AS_EXPRESSION.on(element.ifKeyword))
                 }
                 else {
                     checkImplicitCastOnConditionalExpression(element)

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -776,7 +776,7 @@ public interface Errors {
 
     DiagnosticFactory0<KtElement> SENSELESS_NULL_IN_WHEN = DiagnosticFactory0.create(WARNING);
 
-    DiagnosticFactory0<KtIfExpression> INVALID_IF_AS_EXPRESSION = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<PsiElement> INVALID_IF_AS_EXPRESSION = DiagnosticFactory0.create(ERROR);
 
     // Nullability