Remove error diagnostic from return in multideclaration

#KT-5100 Fixed

compiler/testData/codegen/box/multiDecl/returnInElvis.kt

@@ -0,0 +1,22 @@
+data class Z(val p: String, val k: String)
+
+
+fun create(p: Boolean): Z? {
+    return if (p) {
+        Z("O", "K")
+    }
+    else {
+        null;
+    }
+}
+
+fun test(p: Boolean): String {
+    val (a, b) = create(p) ?: return "null"
+    return a + b
+}
+
+fun box(): String {
+    if (test(false) != "null") return "fail 1: ${test(false)}"
+
+    return test(true)
+}