GrGLGpu: Fix typo in 'if' check

We were checking 'externalType' twice, and never checking
'internalFormat'.  We now check each of them once.

Change-Id: Iae0578a4828fd2a9224e4924245bea0708d8c931
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/227028
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 4e0ce88..1c134f2 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -1619,7 +1619,7 @@
         GrGLenum internalFormat = this->glCaps().getTexImageInternalFormat(format);
         GrGLenum externalFormat = this->glCaps().getBaseInternalFormat(format);
         GrGLenum externalType   = this->glCaps().getFormatDefaultExternalType(format);
-        if (!externalFormat || !externalType || !externalType) {
+        if (!internalFormat || !externalFormat || !externalType) {
             return -1;
         }