Fix empty input string for MeasureTextEx (#4448)

Author: mpv-enjoyer

src/rtext.c

@@ -1327,7 +1327,7 @@ Vector2 MeasureTextEx(Font font, const char *text, float fontSize, float spacing
 
     if (tempTextWidth < textWidth) tempTextWidth = textWidth;
 
-    textSize.x = tempTextWidth*scaleFactor + (float)((tempByteCounter - 1)*spacing);
+    if (size > 0) textSize.x = tempTextWidth*scaleFactor + (float)((tempByteCounter - 1)*spacing);
     textSize.y = textHeight;
 
     return textSize;