Check that the DeapexerInfo was actually set

Otherwise we could return empty DeapexerInfos. We're not running into
any problems due to this at the moment, it's just something I noticed.

Bug: None
Test: m nothing --no-skip-soong-tests
Change-Id: I903d86740a9f22574a5f6bf2effa912bd8237ab6
diff --git a/android/deapexer.go b/android/deapexer.go
index 61ae64e..dcae3e4 100644
--- a/android/deapexer.go
+++ b/android/deapexer.go
@@ -181,7 +181,11 @@
 			// An err has been found. Do not visit further.
 			return
 		}
-		c, _ := OtherModuleProvider(ctx, m, DeapexerProvider)
+		c, ok := OtherModuleProvider(ctx, m, DeapexerProvider)
+		if !ok {
+			ctx.ModuleErrorf("Expected all deps with DeapexerTag to have a DeapexerProvider, but module %q did not", m.Name())
+			return
+		}
 		p := &c
 		if di != nil {
 			// If two DeapexerInfo providers have been found then check if they are