GUI: fix ES5506 Amiga pitch warning

src/gui/sysConf.cpp

@@ -1296,9 +1296,11 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
       if (ImGui::Checkbox(_("Amiga-like pitch (non-linear pitch only)"),&amigaPitch)) {
         altered=true;
       }
+      if (amigaPitch && e->song.linearPitch==2) {
         if (ImGui::IsItemHovered()) {
           ImGui::SetTooltip("pitch linearity is set to linear. this won't do anything!");
         }
+      }
       popWarningColor();
 
       if (altered) {