AP_ICEngine: Initialize start_chan_last_value and catch RC values less than 800

libraries/AP_ICEngine/AP_ICEngine.cpp

@@ -171,7 +171,7 @@ void AP_ICEngine::update(void)
         // while ignoring tiny noise
         if (cvalue >= 1700) {
             cvalue = 2000;
-        } else if (cvalue <= 1300) {
+        } else if ((cvalue > 800) && (cvalue <= 1300)) {
             cvalue = 1300;
         } else {
             cvalue = 1500;

libraries/AP_ICEngine/AP_ICEngine.h

@@ -123,7 +123,7 @@ private:
     AP_Int16 options;
 
     // start_chan debounce
-    uint16_t start_chan_last_value;
+    uint16_t start_chan_last_value = 1500;
     uint32_t start_chan_last_ms;
 };