Fixed use of nvglImageHandlexx in GL utils from earlier PR

- nvglImageHandle was changes to contain GL postfix, changed GL utils
to use that too
- fixed silly failure check bug in FBO demo

example/example_fbo.c

@@ -175,7 +175,7 @@ int main()
 		return -1;
 	}
 
-	if (!loadFonts(vg) == -1) {
+	if (loadFonts(vg) == -1) {
 		printf("Could not load fonts\n");
 		return -1;
 	}

src/nanovg_gl_utils.h

@@ -64,7 +64,17 @@ NVGLUframebuffer* nvgluCreateFramebuffer(NVGcontext* ctx, int w, int h, int imag
 	memset(fb, 0, sizeof(NVGLUframebuffer));
 
 	fb->image = nvgCreateImageRGBA(ctx, w, h, imageFlags | NVG_IMAGE_FLIPY | NVG_IMAGE_PREMULTIPLIED, NULL);
-	fb->texture = nvglImageHandle(ctx, fb->image);
+
+#if defined NANOVG_GL2
+	fb->texture = nvglImageHandleGL2(ctx, fb->image);
+#elif defined NANOVG_GL3
+	fb->texture = nvglImageHandleGL3(ctx, fb->image);
+#elif defined NANOVG_GLES2
+	fb->texture = nvglImageHandleGLES2(ctx, fb->image);
+#elif defined NANOVG_GLES3
+	fb->texture = nvglImageHandleGLES3(ctx, fb->image);
+#endif
+
 	fb->ctx = ctx;
 
 	// frame buffer object