Battery: print error info instead of nan% ( macOS )

Author: CarterLi

src/detection/battery/battery_apple.c

@@ -27,13 +27,23 @@ const char* ffDetectBatteryImpl(FFinstance* instance, FFlist* results)
         }
 
         bool boolValue;
+        const char* error;
 
         BatteryResult* battery = ffListAdd(results);
         ffStrbufInit(&battery->capacity);
         int currentCapacity, maxCapacity;
-        if(!ffCfDictGetInt(properties, CFSTR("CurrentCapacity"), &currentCapacity) &&
-            !ffCfDictGetInt(properties, CFSTR("MaxCapacity"), &maxCapacity))
-            ffStrbufAppendF(&battery->capacity, "%.0f", currentCapacity * 100.0 / maxCapacity);
+
+        if ((error = ffCfDictGetInt(properties, CFSTR("MaxCapacity"), &maxCapacity)))
+            return error;
+        if (maxCapacity <= 0)
+            return "Querying MaxCapacity failed";
+
+        if ((error = ffCfDictGetInt(properties, CFSTR("CurrentCapacity"), &currentCapacity)))
+            return error;
+        if(currentCapacity <= 0)
+            return "Querying CurrentCapacity failed";
+
+        ffStrbufAppendF(&battery->capacity, "%.0f", currentCapacity * 100.0 / maxCapacity);
 
         ffStrbufInit(&battery->manufacturer);
         ffStrbufInit(&battery->modelName);