Improved the error message given when jpeg, TGA, and BMP images fail to decode.

src/modules/image/magpie/ImageData.cpp

@@ -124,10 +124,7 @@ void ImageData::decode(love::filesystem::FileData *data)
 	// The decoder *must* output a 32 bits-per-pixel image.
 	if (decodedimage.size != decodedimage.width*decodedimage.height*sizeof(pixel))
 	{
-		if (decodeHandler)
-			decodeHandler->free(decodedimage.data);
-		else
-			delete[] decodedimage.data;
+		decoder->free(decodedimage.data);
 		throw love::Exception("Could not convert image!");
 	}
 

src/modules/image/magpie/STBHandler.cpp

@@ -75,7 +75,12 @@ FormatHandler::DecodedImage STBHandler::decode(love::filesystem::FileData *data)
 	                                 &comp, 4);
 
 	if (img.data == nullptr || img.width <= 0 || img.height <= 0)
-		throw love::Exception("Could not decode image with stb_image.");
+	{
+		const char *err = stbi_failure_reason();
+		if (err == nullptr)
+			err = "unknown error";
+		throw love::Exception("Could not decode image with stb_image (%s).", err);
+	}
 
 	img.size = img.width * img.height * 4;