GL: Properly reset FBO after emulated blit (#2782)

Reset the previously bound FBO after rendering an emulated blit instead
of binding the default framebuffer.

Co-authored-by: Sami Kyöstilä <sami.kyostila@unrealvoodoo.org>

src/renderer_gl.cpp

@@ -7182,7 +7182,7 @@ namespace bgfx { namespace gl
 					) );
 
 				GL_CHECK(glDeleteFramebuffers(1, &fbo) );
-				GL_CHECK(glBindFramebuffer(GL_FRAMEBUFFER, 0) );
+				GL_CHECK(glBindFramebuffer(GL_FRAMEBUFFER, m_currentFbo) );
 			}
 		}
 	}