Fix out of bounds read in sccp

Author: nikic

ext/opcache/Optimizer/sccp.c

@@ -2329,6 +2329,7 @@ static int try_remove_definition(sccp_ctx *ctx, int var_num, zend_ssa_var *var,
 				if (opline->opcode == ZEND_DO_ICALL) {
 					removed_ops = remove_call(ctx, opline, ssa_op);
 				} else if (opline->opcode == ZEND_TYPE_CHECK
+						&& ssa_op->op1_use >= 0
 						&& !value_known(&ctx->values[ssa_op->op1_use])) {
 					/* For TYPE_CHECK we may compute the result value without knowing the
 					 * operand, based on type inference information. Make sure the operand is