Resolve GCC error (#4750)

This commit withouc cpp change should *fail* CI since it activates the warning
in question

So then correct the build error which Release exposes on gcc8

Closes #4748

azure-pipelines.yml

@@ -95,8 +95,8 @@ jobs:
         imageName: 'ubuntu-20.04'
         isLinux: True
         needsLV2: True
-        cmakeArguments: "-DCMAKE_BUILD_TYPE=Debug -DJUCE_SUPPORTS_LV2=True -DSURGE_ALTERNATE_JUCE=libs/JUCE-lv2"
-        cmakeConfig: "Debug"
+        cmakeArguments: "-DCMAKE_BUILD_TYPE=Release -DJUCE_SUPPORTS_LV2=True -DSURGE_ALTERNATE_JUCE=libs/JUCE-lv2"
+        cmakeConfig: "Release"
         cmakeTarget: "surge-xt_LV2"
 
   pool:

src/gui/SurgeGUIEditorValueCallbacks.cpp

@@ -43,13 +43,13 @@ void decode_controllerid(char *txt, int id)
     switch (type)
     {
     case 1:
-        snprintf(txt, TXT_SIZE, "NRPN %i", num);
+        snprintf(txt, 16, "NRPN %8i", num);
         break;
     case 2:
-        snprintf(txt, TXT_SIZE, "RPN %i", num);
+        snprintf(txt, 16, "RPN %8i", num);
         break;
     default:
-        snprintf(txt, TXT_SIZE, "CC %i", num);
+        snprintf(txt, 16, "CC %8i", num);
         break;
     };
 }