Merge pull request #1639 from AnHardt/warning5

G4 could wait for an undefined time

Marlin/Marlin_main.cpp

@@ -1690,7 +1690,7 @@ inline void gcode_G2_G3(bool clockwise) {
  * G4: Dwell S<seconds> or P<milliseconds>
  */
 inline void gcode_G4() {
-  unsigned long codenum;
+  unsigned long codenum=0;
 
   LCD_MESSAGEPGM(MSG_DWELL);