[wasm] Do not produce code for br_if if its condition does not validate.

src/wasm/ast-decoder.cc

Index: src/wasm/ast-decoder.cc
diff --git a/src/wasm/ast-decoder.cc b/src/wasm/ast-decoder.cc
index 48db8e9e68089e74f6fe6a8b42cadd353178a3dd..7dffef2649ff986d5a01921e3ff70861d07ec780 100644
--- a/src/wasm/ast-decoder.cc
+++ b/src/wasm/ast-decoder.cc
@@ -1023,7 +1023,7 @@ class WasmFullDecoder : public WasmDecoder {
             Value cond = Pop(operand.arity, kAstI32);
             Value val = {pc_, nullptr, kAstStmt};
             if (operand.arity == 1) val = Pop();
-            if (Validate(pc_, operand, control_)) {
+            if (ok() && Validate(pc_, operand, control_)) {
               SsaEnv* fenv = ssa_env_;
               SsaEnv* tenv = Split(fenv);
               fenv->SetNotMerged();