Convert to expression body is forbidden for if without else #KT-12951 Fixed

idea/testData/intentions/convertToExpressionBody/elvisIfElseUnit.kt

@@ -0,0 +1,9 @@
+// IS_APPLICABLE: true
+
+fun nullable() {}
+
+fun bar() {}
+
+fun foo(f: Boolean) {
+    <caret>nullable() ?: if (f) bar() else bar()
+}