several sanity checks added

src/cpu.cpp

@@ -49,7 +49,10 @@ void update(cpuSensors* c) {
         utils::fastReadNum<1000>("/sys/devices/system/cpu/cpu" + std::to_string(i) + "/cpufreq/cpuinfo_avg_freq", buf, t);
         c->avg_freq += t;
     }
-    c->avg_freq /= c->num_cores;
+    c->avg_freq /= (c->num_cores > 1) ? c->num_cores : 1;
+
+    if (c->hwmon.empty())
+        return;
 
     // commented out unused values so its faster
     if (c->module == zenpower) {

src/gpu.cpp

@@ -102,12 +102,15 @@ void updateFromMetrics(gpuSensors* g) {
 
 /* reads values from system and updates the target gpu::sensors struct */
 void update(gpuSensors* g) {
-    fillMissingMetrics(g);
+    const bool hwmon_valid = !g->hwmon.empty();
+    if (hwmon_valid)
+        fillMissingMetrics(g);
 
     if (g->hasGpuMetrics)
         updateFromMetrics(g);
     else
-        updateFromFs(g);
+        if (hwmon_valid)
+            updateFromFs(g);
 
     if (g->fan_speed > 9999) g->fan_speed = 9999;  // sanity check fan speed
 }