overlay: hide ram_temp when no RAM temperature sensor is present

ram_temp is read from an spd5118 hwmon sensor. With no such sensor, like
on handhelds, mem_temp stays 0 and the "full" layout shows a bogus "0 C".

Track whether a sensor was found and only draw ram_temp when one is, so
a real 0 C reading still shows.

Author: matte-schwartz

src/hud_elements.cpp

@@ -778,7 +778,8 @@ void HudElements::ram(){
         ImGui::PopFont();
     }
 
-    if (HUDElements.params->enabled[OVERLAY_PARAM_ENABLED_ram_temp]) {
+    // only when an spd5118 RAM temp sensor exists, else mem_temp is a bogus 0
+    if (HUDElements.params->enabled[OVERLAY_PARAM_ENABLED_ram_temp] && mem_temp_available) {
         ImguiNextColumnOrNewRow();
         if (HUDElements.params->enabled[OVERLAY_PARAM_ENABLED_temp_fahrenheit])
             right_aligned_text(HUDElements.colors.text, HUDElements.ralign_width, "%i", HUDElements.convert_to_fahrenheit(mem_temp));

src/memory.cpp

@@ -12,6 +12,7 @@
 
 float memused, memmax, swapused;
 int mem_temp;
+bool mem_temp_available = false;
 uint64_t proc_mem_resident, proc_mem_shared, proc_mem_virt;
 
 void update_meminfo() {
@@ -46,6 +47,7 @@ void update_mem_temp() {
             if (read_line(path + dir + "/name") == "spd5118")
                 mem_temp_files.emplace_back(path + dir + "/temp1_input");
         }
+        mem_temp_available = !mem_temp_files.empty();
         if (mem_temp_files.empty())
             SPDLOG_ERROR("failed to find known ram temp sensors");
     }

src/memory.h

@@ -6,6 +6,7 @@
 
 extern float memused, memmax, swapused;
 extern int mem_temp;
+extern bool mem_temp_available;
 extern uint64_t proc_mem_resident, proc_mem_shared, proc_mem_virt;
 
 void update_meminfo();