typo reported by Panda user bb2

panda/src/glstuff/glGraphicsStateGuardian_src.cxx

@@ -5943,7 +5943,7 @@ update_standard_texture_bindings() {
         GLP(TexEnvi)(GL_TEXTURE_ENV, GL_RGB_SCALE, 1);
         GLP(TexEnvi)(GL_TEXTURE_ENV, GL_ALPHA_SCALE, 1);
         GLP(TexEnvi)(GL_TEXTURE_ENV, GL_SRC0_RGB, GL_TEXTURE);
-        GLP(TexEnvi)(GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR);
+        GLP(TexEnvi)(GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR);
         GLP(TexEnvi)(GL_TEXTURE_ENV, GL_SRC1_RGB, GL_PREVIOUS);
         GLP(TexEnvi)(GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR);
         GLP(TexEnvi)(GL_TEXTURE_ENV, GL_SRC2_RGB, GL_TEXTURE);