New J2K: Fix explicit NPE cases in conversions

nj2k/src/org/jetbrains/kotlin/nj2k/JKSymbolProvider.kt

@@ -83,7 +83,7 @@ class JKSymbolProvider {
             }
         }
 
-    fun transferSymbol(to: JKDeclaration, from: JKDeclaration) = symbolsByJK[from]!!.let {
+    fun transferSymbol(to: JKDeclaration, from: JKDeclaration) = symbolsByJK[from]?.also {
         it as JKUniverseSymbol<JKTreeElement>
         it.target = to
         symbolsByJK[to] = it

nj2k/src/org/jetbrains/kotlin/nj2k/conversions/ImplicitInitializerConversion.kt

@@ -53,7 +53,7 @@ class ImplicitInitializerConversion(private val context: ConversionContext) : Re
             .toMap()
 
         fun JKMethodSymbol.parentConstructor(): JKMethodSymbol? =
-            (symbolToConstructor[this]!!.delegationCall as? JKDelegationConstructorCall)
+            (symbolToConstructor[this]?.delegationCall as? JKDelegationConstructorCall)
                 ?.identifier
 
         val constructors = containingClass.declarationList