[JS IR] Don't assume a single constructor in the Char class

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIntrinsics.kt

@@ -192,7 +192,6 @@ class JsIntrinsics(private val irBuiltIns: IrBuiltIns, val context: JsIrBackendC
     }!!
 
     val charClassSymbol = getInternalClassWithoutPackage("kotlin.Char")
-    val charConstructor = charClassSymbol.constructors.single().owner
 
     val stringClassSymbol = getInternalClassWithoutPackage("kotlin.String")
     val stringConstructorSymbol = stringClassSymbol.constructors.single()

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ConstLowering.kt

@@ -31,7 +31,7 @@ class ConstTransformer(private val context: JsIrBackendContext) : IrElementTrans
         carrierFactory: (Int, Int, IrType, C) -> IrExpression,
         vararg args: C
     ): IrExpression {
-        val constructor = irClass.constructors.single()
+        val constructor = irClass.constructors.single { it.owner.isPrimary }
         val argType = constructor.owner.valueParameters.first().type
         return IrConstructorCallImpl.fromSymbolOwner(irClass.defaultType, constructor).apply {
             for (i in args.indices) {