Fix for chrome fuzzer

TBR=
BUG=skia:

Review URL: https://codereview.chromium.org/801493003
diff --git a/src/gpu/GrBitmapTextContext.cpp b/src/gpu/GrBitmapTextContext.cpp
index fdf9600..2df3a71 100755
--- a/src/gpu/GrBitmapTextContext.cpp
+++ b/src/gpu/GrBitmapTextContext.cpp
@@ -157,7 +157,8 @@
     // if we have RGB, then we won't have any SkShaders so no need to use a localmatrix, but for
     // performance reasons we just invert here instead
     if (!viewMatrix.invert(&fLocalMatrix)) {
-            SkDebugf("Cannot invert viewmatrix\n");
+        SkDebugf("Cannot invert viewmatrix\n");
+        return;
     }
 
     while (text < stop) {
@@ -205,7 +206,8 @@
     // if we have RGB, then we won't have any SkShaders so no need to use a localmatrix, but for
     // performance reasons we just invert here instead
     if (!viewMatrix.invert(&fLocalMatrix)) {
-            SkDebugf("Cannot invert viewmatrix\n");
+        SkDebugf("Cannot invert viewmatrix\n");
+        return;
     }
 
     int numGlyphs = fSkPaint.textToGlyphs(text, byteLength, NULL);