Correct #400 and #402 + other tweaks

Corrected font 2 rendering issue #402
Corrected NULL pointer issue #400
Changed grave ` character (key for this character is left of numeral 1
key) to degree symbol in font 2
Change setup24 so DC pin is not D3

TFT_eSPI.cpp

@@ -2352,7 +2352,7 @@ int16_t TFT_eSPI::textWidth(const char *string, uint8_t font)
       str_width += pgm_read_byte( widthtable + uniCode); // Normally we need to subtract 32 from uniCode
       else str_width += pgm_read_byte( widthtable + 32); // Set illegal character = space width
     }
-    if ((font == 2) && (str_width > 0)) str_width--;
+
   }
   else
   {
@@ -4342,23 +4342,24 @@ int16_t TFT_eSPI::drawChar(uint16_t uniCode, int32_t x, int32_t y, uint8_t font)
     {
       spi_begin();
 
-      setWindow(x, y, (x + w * 8) - 1, y + height - 1);
+      setWindow(x, y, x + width - 1, y + height - 1);
 
       uint8_t mask;
       for (int32_t i = 0; i < height; i++)
       {
+        pX = width;
         for (int32_t k = 0; k < w; k++)
         {
-          line = pgm_read_byte((uint8_t *)flash_address + w * i + k);
-          pX = x + k * 8;
+          line = pgm_read_byte((uint8_t *) (flash_address + w * i + k) );
           mask = 0x80;
-          while (mask) {
+          while (mask && pX) {
             if (line & mask) {tft_Write_16(textcolor);}
             else {tft_Write_16(textbgcolor);}
+            pX--;
             mask = mask >> 1;
           }
         }
-        pY += textsize;
+        if (pX) {tft_Write_16(textbgcolor);}
       }
 
       spi_end();
@@ -4895,6 +4896,12 @@ int16_t TFT_eSPI::drawFloat(float floatNumber, uint8_t dp, int32_t poX, int32_t
 
 void TFT_eSPI::setFreeFont(const GFXfont *f)
 {
+  if (f == nullptr) // Fix issue #400 (ESP32 crash)
+  {
+    setTextFont(1); // Use GLCD font
+    return;
+  }
+
   textfont = 1;
   gfxFont = (GFXfont *)f;