Fix buffer overflow in LCD_disp_str

This buffer overflow occur when right tc offet is >= 10.00 or <=-10.00
in this case, there is 22 chars to be displayed on the line.
This also occur with long version string as v0.5.2-4-dirty-gxxxxxx.
This cause reboot of the firmware.

note from snprintf(3) :
snprintf return the return value is the number of characters (excluding the terminating null byte) which would have  been
written  to the final string if enough space had been available.

src/lcd.c

@@ -86,13 +86,13 @@ void charoutsmall(uint8_t theChar, uint8_t X, uint8_t Y) {
 
 void LCD_disp_str(uint8_t* theStr, uint8_t theLen, uint8_t startx, uint8_t y, uint8_t theFormat) {
 #ifdef MINIMALISTIC
-	for (uint8_t q = 0; q < theLen; q++) {
+	for (uint8_t q = 0; q < theLen && startx<=(FB_WIDTH-6); q++) {
 		charoutsmall(theStr[q], startx, y);
 		startx += 6;
 	}
 #else
 	uint8_t invmask = theFormat & 0x80;
-	for(uint8_t q = 0; q < theLen; q++) {
+	for(uint8_t q = 0; q < theLen && startx<=(FB_WIDTH-6); q++) {
 		charoutsmall(theStr[q] | invmask, startx, y);
 		startx += 6;
 	}