[WASM] Fix invalid fields name section emit

wasm/wasm.ir/src/org/jetbrains/kotlin/wasm/ir/convertors/WasmIrToBinary.kt

@@ -168,9 +168,9 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
             // Experimental fields name section
             // https://github.com/WebAssembly/gc/issues/193
             appendSection(10u) {
-                appendVectorSize(module.gcTypes.size)
-                module.gcTypes.forEach {
-                    if (it is WasmStructDeclaration) {
+                val structDeclarations = module.gcTypes.filterIsInstance<WasmStructDeclaration>()
+                appendVectorSize(structDeclarations.size)
+                structDeclarations.forEach {
                     appendModuleFieldReference(it)
                     appendVectorSize(it.fields.size)
                     it.fields.forEachIndexed { index, field ->
@@ -181,7 +181,6 @@ class WasmIrToBinary(outputStream: OutputStream, val module: WasmModule, val mod
             }
         }
     }
-    }
 
     private fun appendInstr(instr: WasmInstr) {
         val opcode = instr.operator.opcode