fix(fdc): avoid read/write execution phases if no data available

Author: giuliof

src/fdc.c

@@ -260,6 +260,11 @@ static void pre_exec_write_data(void) {
 static uint8_t exec_write_data(uint8_t value) {
     rw_args_t *rw_args = (rw_args_t *)args;
 
+    if (rwcount_max == 0) {
+        LOG_WARN("Write execution happened when no data can be written");
+        return 0;
+    }
+
     exec_buffer[rwcount++] = value;
 
     if (rwcount == rwcount_max) {
@@ -337,6 +342,11 @@ static void pre_exec_read_data(void) {
 static uint8_t exec_read_data(uint8_t value) {
     rw_args_t *rw_args = (rw_args_t *)args;
 
+    if (rwcount_max == 0) {
+        LOG_WARN("Read execution happened when no data can be read");
+        return 0;
+    }
+
     // read doesn't care of in value
     (void)value;
     uint8_t ret = exec_buffer[rwcount++];