Don't allocate args when instruction parsing fails

.. it looks like (opcode == -1) should maybe lead to an error return
rather than a continue, but in any case we need to avoid leaking
'args' in this situation.

.. the previous arrangement lead to compiler diagnostics when
building with 'scan-build make', such as:

libtvm/tvm_parser.c:186:39: warning: Potential leak of memory pointed to by 'args'
        for (line_idx = 0; tokens[line_idx]; line_idx++) {
                                             ^~~~~~~~
1 warning generated.

libtvm/tvm_parser.c

@@ -189,10 +189,13 @@ int tvm_parse_program(
 		int opcode = tvm_parse_instr(
 			vm, tokens[line_idx], &instr_place);
 
+		if (opcode == -1)
+			continue;
+
 		int **args = tvm_parse_args(
 			vm, tokens[line_idx], &instr_place);
 
-		if (opcode == -1 || !args)
+		if (!args)
 			continue;
 
 		void *newptr;